There are a few types of "Suck" that people use. They all vary on the level (ex: suck = 2) The types are on a scale of insults. "Suck" levels determine how much you want to insult the person.
1) Oof
2) Sucks
3) Suks
4) Succs/Succz
5) Sukks/Sukkz
6) Saks/Sacs
7) Sax
8) Sux
SUCK LEVELS:
This oofs! (Mega Clean)
This sucks (Cleanish)
This suks (Mild)
This succs / This succz (Mild Insult)
This sukks / This sukkz (Medium Insult)
This saks / This sacs (Pointing Insult)
This sax (Hurt Intended)
This sux (You Mean It)