No. Abuse is never an appropriate topic, especially when it involves beloved characters from a popular series like Dragon Ball. It goes against the positive values that the series usually promotes.
Fanfictions can vary widely in their themes and content. In the case of 'yamcha abuses bulma fanfiction', it's a rather disturbing concept considering the characters. In the original Dragon Ball series, Yamcha and Bulma have a past relationship that was not like this at all. So this fanfiction might be an attempt by some writer to explore extreme and negative situations, but it's not something that would be considered positive or in - keeping with the general feel of the Dragon Ball franchise.
To my knowledge, there aren't any sad story porn comics with Yamcha. Such content would be quite unusual and may even be against the law in many places.
One possibility is a tale where a seemingly useless man is chosen for a special mission because of a hidden talent no one knew about. Maybe it's a quest to save a kingdom or something like that.
Maybe Yamcha gets a special gaming device that gives him unique powers in the real world, but only when he completes certain in - game quests. So he has to balance his normal life as a Z - Fighter with his new gaming - related adventures. For example, he might need to defeat a powerful in - game boss to gain the power to heal his wounds faster in real battles.
In a Yamcha reincarnation fanfiction, he could be reincarnated as a Saiyan. This would completely change his character arc. He'd have to deal with the Saiyan's natural aggression and warrior instincts. It would be interesting to see how he combines his old Yamcha self with the new Saiyan nature. He might struggle to fit in with the Saiyan society at first, but eventually find his place and become a powerful force among them.
Well, it could be about Yamcha making Bulma cry perhaps because he said something really mean. Maybe he criticized her for being too obsessed with her inventions and not paying enough attention to their relationship.