none of these characters will be a problem beyond green ranks

steve and hwoarang have a hard time breaking turtles (well, save for hwoarangs grab game, but no one in green ranks is going to apply that properly) just spam hellsweep

nina's strings are gimmicks, as soon as you know where to duck parry and step its an easy counter, just study the strings you see hitting you so much

katarina is dangerous in green ranks when you don't know her but overall shes pretty weak, just spam hellsweep

don't get counterhit with negan lol

you arent safe from fahkumram

lucky chloe sucks, only abusable move is the looping string that you can lowparry, if you're getting hit by anything else you deserve it

pick a character that's easier on the execution, dragunov is a decent pick (if you discount iWR moves) but his game is still somewhat annoying to apply, so you'll have to study a lot to win with him. i'd say you should stick with kazuya though, if your execution isn't good enough try find alternate moves you can use that aren't necessarily max damage, but just enough so that you get some reward for your opponents mistake