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.
Acceptable Targets: The series is known for using national stereotypes, as opposed to racial stereotypes. People generally don't seem to be severely offended even though they recognize the stereotypes; the characters seem more cartoonish than realistic.
Breather Boss: In the Wii game, many people find Super Macho Man much easier than the preceding bout against Bald Bull or the following bout against world champion Mr. Sandman.
Don Flamenco is also sandwiched between more difficult fighters in the Wii game (Great Tiger and Aran Ryan), and in the NES original is easier than most of the fighters who preceded him, at least the first time you fight him.
The rematch can catch you off-guard at first, but his punches are fairly easy to dodge once you know they're coming, and it's fairly easy to at least win by decision. He's also sandwiched between the rematch with Bald Bull and Mr. Sandman.
Super Macho Man is sometimes considered a Breather Boss in the NES game as well, as many consider Mr. Sandman, who comes before him, to be a much harder fight. That said, Macho Man is still quite a challenge in the NES game.
Narcis Prince from Super Punch Out also qualifies as this, as he's quite a bit less challenging than Mad Clown and Super Macho Man and much less challenging than the rest of the Special Circuit.
Disco Kid in Title Defense. After the Difficulty Spike in TD Glass Joe and the significantly harder TD Von Kaiser with fake-out punches and a one-hit knockdown punch that requires good reflexes to dodge, Disco Kid is somewhat easier in which he doesn't have any fake-out blows or one-hit knockdowns, having only faster but manageable attacks and two new moves that are fairly easy to get around.
Fanon Discontinuity: Nobody expected the SNES player character to be Little Mac, with many assuming him being labeled such in his guest appearance in Fight Night Round 2 just being EA taking artistic liberties.
Good Bad Bugs: It's unknown whether the strategy of blocking Soda's uppercuts on the NES was intentional or a glitch, but it makes beating him insanely easy.
Ho Yay: Along with the above, Frank Jr. looks positively elated to lose the match. Flushed cheeks, drooling smile, the works.
In the fandom, Little Mac and Narcis Prince seem to be paired up the most.
It's the Same, Now It Sucks: What some people claim about the Wii version compared to the NES version, especially those who have seen but haven't actually played the Wii version.
Memetic Loser: Who's an even bigger loser than Glass Joe? The guy whom Glass Joe got his one and only win against.
Nightmare Fuel: Mr Sandman in the Wii version. Also, Aran Ryan and Bald Bull. All three of them get downright creepy close-up face shots among other things.
You can see your defeat opponents' reactions after beating them in Contender and Total Defense mode. Contender Sandman gives one of the most terrifying death glares ever seen.
In the Wii version, Great Tiger's special K.O. animation has him Teleport Spam before passing out. In Title Defense, at the end he disappears and doesn't come back.
Replacement Scrappy: Quite a few people feel Mr. Dream is a poor substitute for Iron Mike. Doesn't help that Mr. Dream seems generic and not a lot of originality went into him (same body type Tyson had, same exact dialogue, same exact moves, 99-0-99 record, comes from "Dreamland", etc.). At least Nick Bruiser was fairly memorable...
Surprise Difficulty: You wouldn't expect Glass Joe to put up a fight, but once you get to Title Defense...
Tear Jerker: Doc Louis wandering through Little Mac's exhibit in the ending cutscene of the Wii version.
That One Boss: In the Wii version, Title Defense Bald Bull is unanimously considered to be the hardest opponent. Significant damage on every attack, a right uppercut that comes out very quickly, a change in timing on his Bull Charge (his One-Hit Kill), and most importantly, knockdown immunity unless hit with a Star Punch.
It also doesn't help that the Stars are hard to get.
Bald Bull's status as That One Boss is lampshaded in Family Guy when, while praying, Peter asks God for advice on how to beat him.
Soda Popinski in Title Defense. If you don't have quick reflexes, have fun losing. Soda moves very quickly and early on takes little damage. Each consecutive time you counter, he'll take more damage, but if you get hit, it resets. And without quick reflexes, you'll be getting hit a lot.
Dragon Chan in Super Punch Out (arcade and Super NES). Blocks a lot, is fast and has that one hit kill kick.
Especially in the rematch of the arcade game. He blocks a lot more efficiently and he does two of those kicks in a row. Not only is the timing on dodging the kicks difficult, he throws them with random build-up times and if he ends on the player's right he can't be countered after missing.
Great Tiger in the arcade Super Punch-Out!!, especially the rematch. He rarely stuns and even if he does the player gets at most one or two extra punches out of it. He also uses an annoying low hook attack with an odd build-up time making it very hard to dodge or counter. Even worse, he'll dodge the player's attack and follow with an easily avoidable attack, allowing the player to dodge that and get in a hit or two. Great, until he suddenly counters instantly and gets a free hit on the player.
Many people will agree that Mike Tyson is the hardest opponent in the entire series. His quick reflexes & brutal attacks really makes him a challenge.
The Woobie: The Wii version makes you feel sorry for Glass Joe and Von Kaiser (Glass Joe especially).
Look at your defeated opponents gallery in Title Defence. It's hard not to feel sorry for King Hippo with his lip quivering, Bear Hugger looking like he's about to cry, the crushed looks of Disco Kid, Don Flamenco, or Soda Popinski — even Super Macho Man has a face that could inspire some sympathy! The only exceptions are Mr. Sandman (who just looks absolutely stunned), Great Tiger (who simply looks like he's about to puke) and Aran Ryan... who could perhaps use a smoke... And if you felt bad for Von Kaiser before, look at the mess he's become in Title Defence review and his woobism goes through the roof.