You are ignoring WHY he did what he did with the Stormtroopers. He didn't wipe out the stormtroopers for fun or because they were in his way. He agreed to help Din defend Grogu. There was a reason he did it. Just like there is a reason he let Black Krrsantan go.
Seriously, why do you ignore the what the show tells you and fill it with your head canon instead?
Krrsantan was not longer an active threat at the point he was let go because the Twins who he was working for at the time canceled the contract. Boba is not ruthless without reason.