No. Not really
And no, Mangog is not dead. So far he has never been killed. By any character.
How about DD? I hear that is what is does. He dies a Lot. Then he comes back blah, blah and blah.
Mangog has dissipated and shrunk and BFR. That's about it. Even Classic Odin could not kill Mangog.
Well, Mangog is more powerful than Classic Odin, so... oh. He's not?
Well...
How r DD's magic powers working lately? Oh. He doesn't have any? Ok.
Well then, how 'bout that 'Shrink Ray"? Oh. No shrink ray either.
Well, surely DD can disconnect Mangog from all emotion in the universe and dissipate Mangog! Ooohh. Can't do that either.
Well, maybe DD can BFR Mangog. Oh, no BFR.
Well, DD has never been beaten by sheer physical force, so... oh. He has.
Maybe Mangog wont use his strength and his invulnerability wont help him. Oh, but, then he still has energy and matter manipulation, as well as the ability to change shape and possibly teleport over any distance.
Well, maybe Mangog will choke and die while he is eating DD. there's always THAT.