Koukou Butouden Crows

Both are 90s short OVA series that are adaptations of well known mangas about high school boy delinquents being dumb and badass. 

fights with no reason whatsoever , but fun to watch although one is humorous (crows) and other one is kinda dark (Tokyo revengers) they both deliver delinquent ways of life that any delinquent fan enjoys Tokyo revengers is in past which affects the future somewhat serious. P. S. time travel is only used as a tool while crows is normal carefree delinquents throwing hands for fun. 

Both series are school comedies (with a fair share of drama) where the main character is a badass involved in high school gang fights, with similar kind of humour. 

Both animes about delinquents, although Gokusen is funnier with less fighting. I think they might even be set in the same area of Tokyo, since they both feature a really similar bridge.