Badass Normal: With none of Axel or Blaze's firey attacks, Zan's cybernetics or even the Charles Atlas Superpowers of Max or his young brother Skate, Adam holds his own against Mr. X's cyborgs, robots, self cloning samurai ninjas and kangaroos.
Fat Bastard: Not exactly an agile enemy, but you better not try and take advantage of that by throwing or slamming them if you're not Max or Skate. The second game's iteration of him is an exception, though, for whatever reason.
Meaningful Name: If you need an idea of how unpleasant they are, "Onihime" literally translates into "ogre princess". "Yasha" is a term for a certain type of minor deity, but in modern usage (see InuYasha) it just means "demon".
Turns Red: Players of Remake who think they're used to dealing with his old tricks are in for a nasty surprise when he is down to his last lifebar. His stance suddenly changes to holding his tommy gun with only one arm, and he starts using melee moves like the playable characters. He even has a back throw and blitz attacks which, naturally, he can do without restrictions because he's a boss.
Muscles Are Meaningless: Granted, he uses his entire body for leverage, but even so, it's impressive how he can throw the fat mooks just as easily as Max does. Even moreso in 3, where all the adult characters are unable to accomplish that feat.
King Mook: His palette swaps are common in later rounds of the second game. He is also accompanied by similar mooks in the third game (that thankfully only appears in the last 2 rounds) while also gains a new model (see Rocket below).
Promoted to Playable: Can be played as in SOR3 through a cheat code, albeit in a buggy, incomplete state with a limited moveset. Remake does him justice as a proper hidden character (a Game Breaker, unsurprisingly) and even features his SOR2 version seperately.
The Rival: In the remake, dialogue in one path implies that he's this to Axel.