Problem with Jerry is that he picked a task he wasn't truly invested in like Beth and Summer. He did not want to be better at Golf, he just wanted something that would make him look cool.
The scary part about this is, the Meeseeks are the perfect killing machines. They are driven by their desire for non-existence, which motivates them to do their tasks by any means necessary. And they certainly aren't above killing in order to fulfill their task. They can be damaged, but they can't be killed. And the worst part about this? We don't know how many Meeseeks can be summoned from one box, but we do know a whole lot of them can be summoned at once.
For some reason, out of all the events, Mr. MeSeeks was one of the more frightening concepts of this show. It just seemed like a sad slave invention that could very easily go wrong.