Playing through the games and stuff, Chaosmon always stuck out as odd (or should be absurdly powerful).
Sort of like Omnimon, but much different.
Basically, the way its info goes, it's effectively an incomplete DNA evolution. Instead of completely fusing, the two DigiCores still remain intact.
It basically shouldn't exist for all intents and purposes and yet it does.
In that particular picture, it's BantyoLeomon + Darkdramon, but there's also variants like BantyoLeomon + Valdurmon.
Then somehow, someway, you get this guy, UltimateChaosmon:
Which is basically a 4-way fusion of BantyoLeomon + Darkdramon + Valdurmon + Sleipmon (and something resembling a JRPG Final Boss).
Basically, it's absurdly powerful and crazy unstable to a point to where lesser Digimon are just obliterated just by being near it.
Oddly enough, this mon hasn't really shown in much.
(And in case you can't tell, its body is right below its "eyes' which are giant DigiCores.)