That's the problem with introducing characters as bad-ass killers and assassins. The Not-So-Fatal Five and the League of Super-Haven't-Actually-Assassinated-Anyone-Important have the same problem, as does Chesire. Same with Deadpool and Arcade, I'm sure they have a list of kills as long as my arm, but they haven't killed anyone I've ever heard of, or any character that had, like, a name, so I really don't care.
They aren't allowed to kill the heroes, which makes their reputation come off as all smoke and mirrors, as they get spanked time and again by the good-guys.
And then the shiny new 'coolest character ever' like Prometheus or Cassandra Nova or Some-Dude-I've-Never-Heard-Of-and-Will-Never-See-Again end up wracking up amazing body counts to establish their badass rep, while the actual professional killers cry in their fat-free soy mocho lattes, talking about how they coulda been contendahs and 'always a bridesmaid.'
Scourge makes them all look like wimps, and all he blew away was a dozen super-villains that nobody wanted to use anymore anyway. It's like, 'I made my badass rep by blowing away a bunch of Russian mutants that showed up in a single issue of X-Factor, like fifteen years ago!' 'That's nice, dear. Get to the back of the line.'