History YMMV / ArkhamHorror

** [[http://www.arkhamhorrorwiki.com/Ithaqua Ithaqua.]] [[UnskilledButStrong He doesn't have too many checks you have to pass, and the battle is basically a straight-up physical brawl.]] If you use Call Ancient One when you're armed to the teeth, you have a shot at taking him out. Some players will swear by this method and not even bother closing gates if Ithaqua is the Ancient One.

* BigLippedAlligatorMoment: A number of the various encounters possible in the game can become this given there is no coherent plot between moment to moment. You may encounter bizarre characters or weird interactions, but after the card is resolved, most of these oddities cease to exist.
* BreatherBoss: Some of the easier Ancient Ones can make the game significantly simpler to play. In particular Azathoth is one of the easiest given he barely has any actual bearing on the game outside of the Maniac monster or instant-kill during the endgame. For the most part, he does nothing else.

** The [[http://www.arkhamhorrorwiki.com/Hound_of_Tindalos Hound of Tindalos]]; it's one of the few monsters that can attack you in any location, can move anywhere on the board, and if playing a low sanity character (poor Monterey Jack), it's almost impossible to fight, as it will just nuke your brain instantly.

** Dholes. Resistance to both stats, lethal damage, high stats and toughness...the only thing keeping you sane is that it moves normally, meaning you can generally walk around it.

** Patrice herself. In an online count of statistics, Patrice ties with Mandy as investigators that have successfully beaten a game (with or without other people). Though it makes sense in a game about working together to defeat the board, that the most powerful investigators are the support characters.

** Cultists normally are amongst the weakest enemies (having abysmal Toughness and Combat rating), but they have one particularly annoying trait: very good Awareness stat, meaning you often just can't avoid them unless you have very good Sneak and particularly lucky with dice rolls; and if you start combat with even one enemy, you can't move further until your next turn. This is in the game where one lost turn can mean difference between life and death. Some Ancient Ones also provide them with special bonuses, further increasing their annoyance (but usually not to the point of becoming real danger). Expansions introduce other enemies that are also treated as Cultists for the purpose of gaining the Ancient One's special boons, thus making more bats to cut through. Special mention deserves following combos:
*** Cultists of Nyarlathotep, who combine this with being "Endless" (meaning, you never can completely get rid of them).
*** Cultists of Hastur [[AirborneMook can fly]], thus catching you at worst moment possible. Cultists of Glaaki have similar abilities, thanks to being "Stalker" monsters.
*** Cultists of certain Ancient Ones can make life harder even after being killed, by increasing Doom (Yig) or Terror level (Y'Golonac), or by infecting you with potentially lethal parasites (Eihort).
*** When using Tulzscha as Herald, cultists stop blocking the way (due to being considered "Elusive"), but start directly hunting... for seals, which they can destroy if they begin Mythos phase in same location with one, thus delaying your victory. Being a Herald, Tulzscha can be combined with any of above mentioned Ancient One for even more annoying combo.
* ScrappyMechanic: The herald "The Dark Pharaoh" makes using the Exhibit items very dangerous. The risk of being cursed for a trinket that may not be worth the effort can result in a frustrating experience, especially since said curse will continue screwing you over until it's gone (and these are not always easy to remove).
* ThatOneBoss: In general, the Ancient One's are designed to be entirely unfair, and each one has something that can royally screw the party if they're not ready, but some of the Ancient One's are significantly more frustrating even if you know how to prepare for them.

* ThatOneSidequest: finishing the personal stories of certain characters can be extremely difficult depending on the team present, the time the players have to get objectives done, the speed the game is progressing at, and the requirements for the personal story.

** Mandy Thomspon's story requires you to have 5 gates fail to open thanks to Elder Signs. Even with the base game, this is statistically hard to do until you have numerous sealed locations, whereas it isn't hard to get a rumor card that just ruins the terror level and fails her.

* ThatOneBoss:

** [[http://www.arkhamhorrorwiki.com/Glaaki Glaaki]], with all expansions in play, is often considered Atlach-Nacha's stiffest competition for the top spot. Its five unique minions drain the party's supply of items and tokens, it can instantly put them back in play during the final battle, and it feeds on the rapid Terror Track growth of many expansions with its ability to devour all investigators if the track goes above 10.

* GoddamnedBats: Depending on the Ancient One, Cultists can be either this or DemonicSpiders. Expansions introduce other enemies that are also treated as Cultists and gain the Ancient One's special boons, thus making more bats to cut through.
** Some enemies have the "Endless" modifier, meaning they cannot be taken as a trophy. These enemies are usually easy to kill. USUALLY.