Where the fuck are his parents or loved ones?
A normal guy could kidnap them and hold them hostage.
If he has none, get a girl to be romantically involved with him and fake her kidnapping then.
Have him kill himself or go off planet.
>>139019800
This is the guy who lives in a world where every day thousands die due to strange monsters appearing literally anywhere. His parents are probably long dead, and everyone just learns to deal with death.
>>139019800
But then he would get serious.
>>139019844
This, the death rate in saitama universe is really high, its not a surprise he is willing to risk himself fighting monsters even when he was weak as fuck, everyone he loved died long ago.
Why would you want to blackmail Saitama?
If you're a street thug, Saitama won't even notice you.
If you're a monster, even with no Saitama, you still have to deal with the entire Hero Association.
Also it's popular knowledge that Saitama is a little shit that cheated to get his hero rank, why anyone would be worried about him?