Doom's got this.
Thanos might, too. Both have huge egos, and there's sure to be a confrontation with the heroes in both cases, but i think Thanos'd jump the gun.
Doom would do it in more of a "...Do you seriously think I'd explain my master-stroke if there remained the slightest chance of you affecting its outcome? I did it thirty-five minutes ago." Way.
Still egotistical, but smart.