Has DC's Death *ever* done anything impressive? (ending the universe -from the first Book of Magic series- doesn't count; it would probably end without her anyway.)
Lacking any combat evidence, I'm going to assume that -like most of the Endless- she'll just stand there, talking and talking, while Marvel's cosmics (who fight an amazing number of times, considering who and what they are) would likely flatten her. Curbstomp.
The main problem with fighting the various incarnations of Death is that Death can't usually die. Death of the Endless has actually shown that she's going to be around longer than the universe she's the Death of.