Romano being so dysfunctional and broken that simple things like Spain saying hello to Italy before a world meeting will send him into jealous hysterics about how nobody loves him and everyone likes brother more and whine whine blah blah. This flavour of Romano usually comes with the idea that none of his problems are his own fault and he gets to act like an asshole to everyone with nobody ever calling him out on it.

I'm really not a fan of the type of Bad Friends Trio fics in which they're pretty much the pranksters of Europe and go around doings things like painting Austria's piano pink. Prussia, maybe, but I somehow have a hard time imagining all three characters being into this and having this kind of dynamics.