It was very heavily suggested in Invincible #88 that Thragg could kill Allen quite convincingly. Nothing concrete, but the implication seems clear enough. Scans of their stand-off here:
http://mutantstarr.blogspot.co.uk/2012/02/invincible-88.html
I am way, way behind on Invincible since a little while after this issue though, so the status quo might have changed since I fell behind on my reading.
Cheers.
Originally posted by CadenceV2
IMO could go either way. Thragg suggest many things, but Alan has never hit his full limits yet against any one being.
Yeah, Allen himself claimed he was "almost" as strong as a Viltrumite, when he was obviously much stronger then Omni Man, one of the stronger Viltrumites. I don't think he really knows his own strength, since he used to be quite a bit weaker pre regeneration.