FWIW, I'd argue that the Krenim timeship is far more destructive than anything red matter-related.
I kinda disagree with you there, the Krenim ship doesn't really destroy as apposed to erase. The planets hit by the Krenim time ship beam were fine, good as new really. I guess it's "putting an end to existence" vs "erasing from existence". Red matter is definitely more devistating, no one really knows someone ceased to exist (unless you were in Janeway's situation).