I mainly focus on cheap characters since I have made several of those things, occasionally I create joke characters and balanced ones too.
However, I would like to mention what makes a character good imo:
Character's coding isn't copy pasted from others, at least original in some form (SAMSARA is a good example, he makes unique code for each and every character he makes)
Character has a good sounding voice (Not required but encouraged since it gives the character some personality)
Character's AI is at least 4th or 3rd division like, it can be higher level than that if so desired, 5th divs are bleeeeh no thanks, boring and sometimes terribly bad/repetitive AI in 5th divisions.
Character isn't too gimmicky (I do make exceptions though)
Isn't an obligatory Sprite Swap (Though there are exceptions for this too, some are just too different to be classed as a sprite swap like Dee Bee Kaw)
As a bonus, add a few in jokes for some laughs (The_None does this all the time, like the random bonk that happens with Possessed Heita, Twerking Thanos, etc.)