These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Are the Citadel Council stubborn, willingly blind anti-human racists whose incompetence hamstrings Shepard and imperils the galaxy? Or are they, if not quite a Reasonable Authority Figure, open to being convinced about humanity's merits, the threat of the Reapers, and Shepard's plan to stop them if shown enough evidence?
The quarians. A poor, sympathetic, misunderstood people trying to reclaim their homeworld from murderous machines who have sided with some of the greatest villains in the galaxy, or a bunch of racist, vengeful historical revisionists who got off easy after enslaving and attempting genocide on a sentient race?
The geth. A textbook Woobie Species who are just trying to exist peacefully, or a callous bunch of hypocrites who got away with mass murder ages ago and should have karma coming to them today?
Humanity. Is the rest of the galaxy keeping them from rising to power out of jealousy and paranoia? Or do they simply need to learn to make compromises and sacrifices in order to become part of the galactic community, as well as accept that it will take time for them to integrate, much less rise to the top? Furthermore, when the Reapers attack Earth, is the Council callously abandoning them, or are they merely unwilling to commit to a seemingly hopeless battle without adequate preparation?
Fem!Shep gains this reaction particularly when it comes to discussion of women in video games. Most would say she is the best female character ever, even above the likes of Lara Croft ,Samus Aran and Chun Li. Some however argue that since she is basically the same as a male Shepard then she doesn't count as her own character, thus cannot be considered a virtue of feminism or separate from other characters where sex, actions and dialogue are customizable.
Angst? What Angst?: Shepard seems to take the whole being brought back from the dead thing in stride, completely ignoring the philosophical implications of being dead, being brought back to life as a cyborg, or the possible absence of any form of an afterlife. Tends to be Justified as it's Shepard. It should also be taken into account how immediately after being brought back s/he's thrown right into the fight and doesn't especially have to time to think about things. It's also possible that Shepard is suffering from Death Amnesia. Since its never brought up, its impossible to know one way or the other. Finally subverted during the assault on the Illusive Man's base if you play the videos where the Illusive Man discusses Shepard's reconstruction. It turns out that Shepard has been having a pretty serious existential crisis, and it gets turned Up to Eleven when s/he finds out s/he was literally dead. S/He wonders if s/he's just a VI that thinks s/he's Shepard. Shepard's love interest, if present, will be reassuring
Base Breaker: Liara is a commonly used squadmate and adored by a section of the fanbase that ships her and Shepard, but she gets more vitriol poured over her than nearly any other squadmate, due in part to the Character Focus she tends to receive from the developers: She's mandatory in multiple missions in 3 (Three in the base game, four if you have From Ashes), has a DLC focused on her (to the point where your other characters don't even talk at all once she shows up), is the most plot-relevant party member, and is treated as Shepard's best friend in the second and third game, practically Retconning a Shepard who treated her with hostility, or even just ignored her.
In addition, Jack, Miranda, Kelly Chambers, Zaeed Massani, and (especially after the second game) Kaidan and Ashley are all extremely polarizing characters.
Some interesting examples of this within the fandom:
The First Contact War: Some believe that the turians were well within their rights to uphold galactic law and stop an unknown race (humans) from opening more Mass Relays, while others think they were simply trigger-happy and Lawful Stupid for opening fire without explaining any of this first. Likewise, were the turians justified in using deorbited satellites, spacejunk and small meteors to take out ground forces and civilians, or is this simply a case of Values Dissonance at work, since they don't have civilians and consider all individuals in an active warzone to be valid targets?
The Morning War: Some feel that the Quarians were completely well within their rights to preemptively eliminate the Geth, and that the Geth went overboard almost sending them into extinction. The other side felt that the Geth were justified since they were fighting in self-defense, and that the Quarians got hit by Laser-Guided Karma. It all tends to come down to what side of the What Measure Is a Non-Human? scale are you on?
Similarly, The Reveal in 3 that the asari Deliberately withheld a working Prothean beacon to keep themselves ahead of other races. Some argue that they were right to hold the information because few people had the Cipher. Others argue that they were massive hypocrites for holding the beacon after making a law that said you should reveal beacons when found, and that had the asari revealed the information, the Reapers could have been stopped long before they showed up and butchered trillions of people.
While Aria was a popular character in the second game, some players didn't like how Shepard was forced to help her to get the mercenary faction on your side, and how she got a seperate DLC (Omega being seen as So OK It's Average doesn't help).
Broken Base: The film adaptation. Some fans are excited about the further attention it can bring to the series and getting to see the characters in live action, while others are wary about how by necessity it can only follow one of the numerous possible ways to play through the games, possibly imposing it as the canon story.
Cargo Ship: Joker was the last crewman aboard the original Normandy and Shepard has to literally drag him to the escape pod. Even more prevalent in the second Normandy where Joker displays this withEDI who after being unshackled and allowed full control over the ship, effectively becomes the second Normandy.
Contested Sequel: All three games have good scores (with ME2 receiving the most accolades), but each one has gotten steadily angrier fans who don't like the changes made.
Crazy Awesome: You're free to play Shepard as this. Your Shepard can be the sort of person who deals with rude mercs by shoving them out windows, fights Thresher Maws with a pistol, punches annoying reporters, drinks radioactive liqour, and always has a snarky quip for whatever horrific event is occurring. Shepard can show signs of severe mental instability, but often in ridiculously cool ways.
Shepard: (after hearing how Conrad Verner has been basically acting like a weird hobo) Conrad why are you acting like me?
Die for Our Ship: Can be done in-game, no less. Once ME2 was out, some people who preferred the new love interests went back to the first game and let their former love interest die on Virmire. In ME3, some people who didn't like what happened to characters like Thane and Jacob let them die in the Suicide Mission.
Doing It for the Art: Sure, BioWare didn't need to go so in-depth in the Codex, but it helps expand the world a lot. For example, quarians are all vegetarians - but only because animals take up space and resources. When they land in a system with dextro-DNA animals, they pig out and get the equivalent of a hangover. A lot of fans would never bother to read this in the Codex, but BioWare did it so that if some random Joe wonders about the eating habits of the quarians, they know.
Renegade Shepard. A Knight Templar and Psycho for Hire who indulges in many acts of pointless cruelty and brutality, is a Jerkass to everyone around him/her, murders innocent civilians, is a CerberusFanboy in 2, and can wipe out up to four sentient species during the course of the trilogy (and will wipe out at least two in the rachni and the krogan). And yet in spite of all of that, people praise Renegade Shepard as a Badass and a "real" hero who does what is "necessary" to get the job done even though Paragon Shepard continually proves that there is a better way that Renegade Shepard chooses not to take.
Cerberus. Human-centric terrorists who engage in many Scientific Sins without a second thought. In the first game and the Expanded Universe, they are responsible for loads of victims of brutal experiments - not to mention the cold-blooded murder of Admiral Kahoku, a kindly career soldier Shepard could easily call a friend, for discovering one of their hideouts. And, in the second, they rescue you, replace your Cool Starship, and provide loads of information and money as they believe in your mission of stopping the Reapers. Inevitably, some people focus far more on the latter than the former, to the point that they wonder why people view Cerberus as the villains even though there are still things in the second game (like say, Project Overlord and Jack's Cold-Blooded Torture]]) that remind you that Cerberus aren't good guys. Miranda does give some counterarguments and excuses for some of Cerberus' actions (some more valid than others), but you never do get to ask about any of the other things Cerberus has done, including what was done to Gillian and the various assassinations Cerberus has been behind, or anything about what was done to Kahoku, or what Cerberus was doing with that rogue VI on a military base on Luna - who was, as established in an easy-to-miss conversation, actually a real AI named Hannibal.
In particular, The Illusive Man is clearly meant to be a morally ambiguous (if not outright villainous) figure, but some fans consider him to be a Big Good because he's the only authority figure willing to and capable of helping Shepard fight the Reapers. Mass Effect 3 reveals this to be an invoked trope; In a dossier, it's revealed the The Illusive Man purposely put people like Jacob, Kelly, Gabby, and Kenneth on your crew in order to invoke your sympathies and make Shepard question whether they were truly evil.
Escapist Character: This trope is Commander Shepard to a tee. You can choose to be the ultimate hero or the ultimate bad ass, you can customize Shepard to be most like yourself, most of the characters have a crush on you, and you go around saving the world and kicking ass, as well as becoming an intergalactic celebrity on a regular basis.
Ending Aversion: The third game does that for the entire trilogy, if the official forums are of any significant indication.
The Mass Effect series seems to be one of those unique works that has several Ensemble Darkhorses. Captain Kirrahe, Kal'Reegar from Mass Effect 2, and Matriarch Aethyta are specific examples.
Perhaps the strongest example is Aria T'Loak. She became so popular, developers had a Mass Effect 3 DLC made where she's the star and promoted from NPC to playable character.
Eve in 3, who gives players a glance at what a stable krogan society might look like.
Epileptic Trees: Exactly who is Liara's father has been up for debate for a while. Lair of the Shadow Broker heavily implies that her father is the Asari Bartender, which is confirmed in Mass Effect 3.
Fanon Discontinuity: The maintainers of the primary Mass Effect wiki do not consider the events of Mass Effect: Deception to be canon, which is why Gillian Grayson's entry does not mention her death at the hands of Kai Leng.
The Indoctrination Theory rejects most of the ending of Mass Effect 3 as a Reaper induced hallucination.
There's a fan mod that simply ends the game with Anderson's death, with the assumption that Shepard dies there too.
Likewise, another mod goes so far as to completely re-write everything after the Illusive Man's death by having Shepard's crewmates storm the Citadel to rescue him/her and having the Reapers be destroyed without losing the geth and EDI.
Thane fans have released a mod that overhauls his storyline so that he no longer takes part in the attempted Citadel coup and no longer dies to Kai Leng. Depending on which version of the mod is installed, he can even be cured of Kepral's and gained as a War Asset. Unlike the above mods this one relies on player actions to trigger the altered content—fail to talk to him or do a certain quest, and canon proceeds as normal.
"Funny Aneurysm" Moment: During one of the conversations with Ashley in the first game, when Shepard walks in on her talking with one of her sisters and the sister comments on Male Shepard/Kaidan (depending on Shepard's gender) being "cute," Ash winds up saying "Ohh, shoot me now," out of embarrassment. If Ashley is the Virmire survivor, guess what happens if you aren't able to talk her down in Mass Effect 3?
Goddamned Bats: Husks, unless you're playing a biotic class or something with shotguns. They come at you in packs of five to ten, surround you and pummel you with stunning punches until you die. And another class of Husks (called "Abominations") explode.
In Mass Effect 1, on Virmire, Saren talks about how giving in to the Reapers might be the best choice, and if the Protheans became servants to the Reapers, they might still be around. In Mass Effect 2, the Collectors are Protheans, servants under the Reapers. Ouch.
And in the third game's ending, one of the options is to make Saren's dream of uniting synthetic and organic life true. It is seen by some as the best ending, because it's the one with the highest prerequisites apart from Shepard living in the Destroy ending.
For those that played the "Bring Down the Sky" DLC for Mass Effect 1... well, tables get turned in Arrival, and you're now in the spot Balak was, though for different reasons.
Inverted in the third game. When you talk to Engineer Adams, he tells you about a design flaw with the Normandy's drive core that could lead to someone getting vaporized if the shields take too much fire. It's harsh because if you didn't get Tali's shield upgrade in the second game, that was exactly what killed her (or one of your other squadmates).
Wrex's elevator chatter with Kaidan takes on a dark twist in the third game. Specifically, he asks Kaidan who would win in a fight between him and Shepard, and figures that Shepard would win because Kaidan says he could never imagine fighting his superior officer. Come the third game, if Kaidan survived Virmire, the two of them end up in a standoff that could result in either Shepard or a squadmate taking Kaidan down in one shot. Seems Wrex was right.
Hilarious in Hindsight: Wrex recalls it in the Citadel DLC, where just before fighting Shepard's clone, Wrex will remind Kaidan that now we'll get to find out.
In the first game, if you look at the krogan monument with Tali and Wrex as your squadmates, Tali will complain about the krogan having a monument on the Presidium for their war against the rachni in spite of their later rebellion, while the quarians have nothing. Wrex then replies that in one or two centuries, that monument may be the only proof the krogan existed. If you don't cure the genophage, the ending image implies that the krogan go extinct, proving Wrex correct. If you side with the geth, the quarians are annihilated, perhaps showing to Wrex that the krogan are fortunate by comparison, or at least survive for longer.
Considering some of the possible endings of Mass Effect 3, the line from the credits song ("M4 Part II" by Faunts) "I...have wondered about you...where will you be...when this is through?" is rather painful. Only one ending (Destroy, in which Shepard can survive if your war assets are high enough) allows the possibility of Shepard seeing her/his love interest again.
At the end of the first game, Shepard's companions start to mourn them when the appear to have been killed, only for Shepard to climb out of the wreckage, alive and triumphant. However, less than a month later and at the start of the second game, Shepard really is killed when the Normandy is destroyed and they stay dead for the next two years (and twelve days). And at the end of the third game, unless Shepard chooses Destroy with high EMS, Shepard dies once and for all.
Heartwarming In Hindsight: In the third game, if you do the Tuchanka Bomb mission arc after the Citadel attack, recruit Ashley/Kaidan, and Primarch Victus' son sacrifices himself to disable the bomb, Tali will talk with Ashley or Kaidan, saying it reminded her of Virmire and asking her how she can accept someone dying for her. Ashley/Kaidan says s/he would have done the same, and that one day, it will be Tali's turn. This is both an example of Ashley/Kaidan overcoming his/her Survivor Guilt, and quite comforting to Tali in light of her mission on Haestrom.
Tali also implies that she's worried she won't live up to her father, who is a quarian Admiral. In the third game, she's not only made Admiral entirely on her own merits, but she's also likely to be one of the Admirals that wins back the quarian homeworld. Hard to beat that! Also Harsher in Hindsight, however, because we find out in ME2 that her father was conducting very dangerous experiments with live geth - not really something Tali would want to live up to; while drunk, she laments that her goal in life went from wanting to live up to her father to wanting to make up for his mistakes, and for all she dislikes Miranda, she respects her refusal to let her father control her life.
Hilarious in Hindsight: When speaking with Jacob a little while after his loyalty mission, you can say that the next Normandy needs a lounge. With the Kasumi DLC, her room has a bar. Better yet, the bar is one of the few things that did not get removed when the Normandy ended up in Alliance hands!
Male!Shep and Kaidan were so blatant it was made canon in the third game.
Tali would gladly link suits with Fem!Shep, something she tells Male!Shep is a sign of intimacy among quarians, downloads books on human body language and courtship regardless of Shepard's sex, and in Citadel can even express interest in a threesome with Fem!Shep and Garrus.
Hype Aversion: Most people agree that the Mass Effect games are as good as the reviews and ads say they are.
Fans who were looking forward to buy the Wii U version of Mass Effect 3 were not happy when EA announced that they would release a full Mass Effect collection for the Xbox 360, PC, and PS3 with no Wii U release in sight.
It turned into bigger outrage when it was announced that not only that the Trilogy Collection releases earlier, but it's cheaper than the Wii U's Mass Effect 3. So in other word, a collection that is three games in one, is more cheaper than a single game in the same series.
It Was His Sled: The Protheans didn't build the Mass Relays or the Citadel, it was the Reapers, who are race of space ships that mind control organics and look like robot squids, and Sovereign is a Reaper, not a Reaper ship. This comes as a twist, but is pretty common knowledge amongst the series fans.
Renegade Shepard can potentially be this, if given a Freudian Excuse in the Colonist and/or Sole Survivor background and also have him/her lose most of their crew. Renegade Shepard also suffers from stress and nightmares in 3 just as badly as any Paragon.
Miranda Lawson. "Created" by a raging Narcissist of a father in his attempt to have the "perfect" heir. This results in her being tortured over the manner of her conception (which could make a person pretty existential), had to live up to her father's ridiculously high standards, couldn't get anything without a catch, and worst of all is unable to conceive a child when she wants desperately to be a mother. All of this combines to make it easy to see why she can be an Ice Queen sometimes. It gets taken even further in 3, where she's now on the run from the group she used to passionately serve, is trying to find her sister, and can potentially die in Shepard and her sister's arms. Even worse if you romance her and then dump hercursing her to die no matter what.
Both the geth and the original quarians during the Morning War and in modern times. Both sides were effectively responsible for attempted genocide of the other - though the quarians believed they were only destroying mostly non-sapient machines - and both sides are carrying the war on into the present day. Modern quarians are steeply divided on whether or not to destroy the geth or attempt peace with them (with some verging into full-on General Ripper aggression against the geth), while the geth, while expressing a desire for peace with the quarians, are still aggressively self-defensive and will attack any organic intruding into their territory, including quarians. And ultimately, one side or the other will finish the genocide in Mass Effect 3 unless Shepard intervenes. Yet none of this changes the fact that both sides are viewed as highly sympathetic, and the destruction of either, or potentially both is a very tragic scene.
Launcher of a Thousand Ships: Shepard of both genders has been shipped with everyone. It probably helps that he/her can indeed be shipped with quite a few different characters in the games proper.
Magnificent Bastard: A pure Renegade Shepard. S/he's a total Jerkass to just about everyone, and is incredibly ruthless in getting what s/he wants, and we love him/her for it. The "Renegade" ending of the first Mass Effect definitely takes the cake, A full on Renegade Shep will admit to leaving the Council to die for the sole purpose of replacing them with an all human Council.
Garrus, too, after the second game explored his Character Development further and established just how skilled he was with the sniper rifle. And in-universe, there's nary a soul that can deny his skill at calibrations.
The dev team probably meant for Shepard's N7 armor to be iconic, but they probably didn't expect it to be this popular.
Memetic Sex God(dess): What with the sheer number of people who show interest in Shepard, male OR female, this is pretty much canon.
Memetic Molester: Canonically, Harbinger wants to dominate Shepard utterly, body and soul, so this was bound to happen. It doesn't help that many of his combat taunts sound vaguely sexual (that voice notwithstanding, this goes firmly in the No Yay category, especially when he talks about wanting to preserve Shepard's body).
Ron the Death Eater: On the flipside of Renegade!Shepard's Misaimed Fandom (who romanticize him/her as the ultimate badass), the same fans will vilify the Paragon for being overly idealistic and putting too much blind trust in others. There was even something of a meme with them saying "You should've saved the Collector's base. The irony in all of this being that a Renengade who constantly choose to Shoot the Dog finds themselves with less resources and The Illusive Man stabbing them in the back.
Ambassador Udina. No one likes him, though it is assuredly intentional by BioWare. Makes the potential of Anderson punching him in the face to be undeniably enjoyable by all. And in the third game, you get the chance to kill him in a Renegade interrupt.
Khalisah al-Jilani. Attempts to twist Shepard's words no matter what (s)he says. This is another one that's definitely intentional. Everybody loves punching her out. There are no exceptions. Shepard, Grunt, Hackett, Fem!Shep's voice actor, it doesn't matter. Seeing the Shadow Broker spy cam footage where she is punched by a krogan and kicked in the shin by a volus confirms that the feeling is universal. Even players who surpress the urge to deck her generally take great pleasure in, as Khalisah herself puts it, bullrushing her on her own show.
Councillor Sparatus, the turian council member who always takes a Commander Contrarian opinion, no matter what Shepard does.
Jacob Taylor, who is arguably the least liked squad member in the series (with the exception of Morinth) for a number of reasons. In 2, he's The Generic Guy in a group of incredibly diverse and complex characters, so he's often seen as incredibly boring. Along with that, he's a Master of None with no exceptional skills gameplay-wise. His romance is typically seen as the most poorly handled in the series and, on top of that, while other possible Scrappy characters have a good chance of being rescued by the third game, Jacob cheats on you if you romanced him and justifies it with a very poor excuse. In the Citadel DLC, an unamused female Shepard can respond to this by bitch-slapping him in the face.
Kai Leng, ultimate emperor of the Cutscene Power to the Max. It's common to hear him being called Kai Lame. And unlike some other bosses like Tela Vasir, the fights against him are widely considered to be either uninteresting (for the first one) or challenging, but only because his flunkies are very dangerous. On the other hand, this makes the Renegade Interrupt where Shepard guts him with his/her Omnitool that much more satisfying and popular, even among Paragon players.
The third game gives us Diana Allers, an obnoxious, bland reporter who replaces fan-favorite Emily Wong. She contributes little to nothing to the game, her voice actress is suspected to have only been hired as a favor to IGN, and is just generally unlikable to many players. Fortunately if you really don't like her, you can kick her off the ship.
The Mako. As far as the non-human variety go it gets a bad rep due to its lousy controls, mediocre navigation, poor defense system, and below average aiming system. Doesn't help that in some missions you are forced to travel in one of those so ditching The Mako is out of the question
Not that common in the ME community, mostly because the portrayal through acting and writing makes each love interest as canon as the next, but there are some foolhardy souls who deliberately try to incite flame wars over these things. In particular is the Talimancer group, with especially rabid supporters (or haters) trying to stir things up for no apparent reason.
Played a bit more straight since ME3. Fans of the ME2 romances are not pleased with how those romantic subplots ended in the trilogy, and a grass-is-always-greener effect has each ship arguing that their ship is the most mistreated. One contentious issue is that if you did not romance Kaidan or Ashley, the pre-Extended Cut ending always seems to assume you romanced Liara.
Strangled by the Red String: It was impossible to avoid triggering the romance flag for Liara in ME1 which leads to other crew members (including your love interest) question your interest in her, even if you were openly hostile. Later games had a strong focus on Liara as a love interest, as well as in external media, which made a lot of people turn on her as a potential love interest.
Villain Decay: Husks, just compare them in Mass Effect 1 to Mass Effect 3, and note especially how Shepard deals with them. In one, it took a lot of backing away from them and spamming bullets and avoiding melee like the plague. In the other, Shepard actually quite literally stomps its head to the curb. The second game mixes it up. They're really easily dispatched with any kinetic attack (be it Concussion Shot or Push or Shockwave) unless you're playing on Insanity, which gives them a thick layer of armor. Instant Demonic Spiders.
A better example are the Mass Effect 1 fans who constantly belittle Mass Effect 2 in every single discussion of the series. Bioware forums obviously, but also on Reddit, Kotaku, Destructoid, 4Chan, Facebook, anywhere with a gaming forum for their voices to be heard, you name it. Again and again and again. This is, in spite of the near-equal love for both games, if Amazon's any indication. This has progressed into a complicated webwork of mutual disrespect and hate now that the third game is out.
They Wasted a Perfectly Good Plot: The rachni. An interesting, truly alien race with build-up as one of the main fighters in the war against the Reapers. In Mass Effect 3, you only get one conversation with the Rachni queen, and then they are never seen again.
The romance arc between female Commander Shepard and Garrus Vakarian could have had a big subplot all its own. Turians and humans aren't very nice to each other, and many of them are racist against each other's species. Throughout the romance, not a single peep is heard about the possible Maligned Mixed Marriage their relationship could cause.
Garrus has had things go pretty badly for him, though he still continues fighting for good. Kelly for her part even wants to give him a comforting hug.
Tali'Zorah. From falling in love with a male Shepard just to see him die, seeing her whole squad wiped out twice, to being put on trial for treason and given the insult of having her ship's name taken away, with the option for being exiled, finding out her father is dead and finding his body and knowing he was responsible for the death of the entire ship he was on, to potentially losing her entire people in the third game.
Liara T'Soni. Persecuted as a child for being pure blood, an unknown father and a mother who is dismissive of her. Then her hero dies in the beginning of the Mass Effect 2. It just keeps going on.
Kelly Chambers. If you don't act fast enough in Mass Effect 2, she dies a horrible death, and if you meet up with her in Mass Effect 3 but yell at her for sending covert reports to the Illusive Man about you, she breaks down crying and then commits suicide with cyanide capsules. She does specifically mention she's having serious nightmares following her near-liquefaction at Collector hands. File this one under PTSD.
The Protheans just couldn't catch a break. They get hunted to extinction. They get mind raped into being thoughtless slaves. And, as a final insult, they get 'modified' into Collectors to serve the genocidal bastards that wiped out their civilisation. The Collector General's expression at the end of ME2 as he reaches out for to Harbinger screams 'Daddy, where are you going?'...just before he gets blown up. After recruiting Javikit turns out they were more of an Iron Woobie species-with a side of jerk.
While not quite on the Prothean's level, the quarians count as well. They've been hunted to near extinction by their own creations, have no planet to live on, and are in extreme poverty. Not only that, but the galactic community at large hates them for things their ancestors did hundreds of years ago, meaning racism against them is incredibly common. As put so eloquently by Tali herself...
Shepard: Maybe it's time for your people to give up on reclaiming your world from the geth.
Tali: You have no idea what it's like! You have a planet to go back to! My home is one hull-breach away from extinction!
Shepard: You've got a place here, Tali. Don't throw it away in a war you don't need.
Tali: "Don't need"? Shepard, if I don't wear a helmet in my own home, I die. A single kiss could put me in the hospital! Every time you touch a flower with bare fingers, inhale its fragrance without air filters, you're doing something I can't!
The rachni count as well, being a peaceful race that was mind raped into slavery by the Reapers and almost completely wiped out in the Rachni Wars. And before that? They were far more peaceful until the Protheans bred them to be combat-worthy because of their survivability traits. The Reapers might not have even gotten interested in them otherwise.
And to some degree, the geth. Created as slaves, they nearly trigger their own genocide by asking the utmost basic of questions ("What am I? Do I have a soul? Why am I here?"). They throw their own creators off of their own home planet and, if Legion is to be believed, want nothing more than to co-exist with organics peacefully. Bit of a shame then that a good third of their population generated a 1 where a 0 was supposed to go, cried "Screw self-development!" and figured worshiping an Eldritch Abomination as a machine god was a good idea, which would have forsaken them once it got what it wanted. Now most of the Council races want them gone too and like the quarians see them as little more than berserk robots.