I kinda see him getting an epic death scene, where by himself he takes down a bunch of monsters.
"We haven't really run into anything that could kill Mister at this point."
Note that
Mr Sunshine had made his appearance by the point that Jim said this.
So in terms of 'Power Levels' Mister>Casual Galaxy Busters
Unless the Prince of Darkness himself shows up for a throw-down, I don't know of any monsters that can actually stop our Feline Overlord.