((UNIVERSAL manipulator. Turn its fissionable material to strawberry pudding.))
((Mm, fissionable strawberry pudding...))
((A small but superdense gravity well should do it.))
((Yeah, nothing can go wrong with making a quasi-black hole! As long as you do it when nothing I care about is on the same planet.))
((It's a LESHO round. Whatever is inside it is really, really nasty. Nasty enough to be shot at an Avatar by itself.
It might work with heat, true, but I just think that it might have internal systems to cope with large amounts of heat already, since it's being fired so fast that it needs to be able to function under the large amounts of energy from air friction alone. I think that he's got a better chance of disarming it by partially transforming part of the insides of the round into some kind of nasty liquid, which would DEFINATELY wreck it if it's a nuke and disarm it with a higher chance of success.))
((Air resistance would be dealt with via simple heat shields
on the outside; that would be the simplest way to heat it.
And yeah, turning the insides into caustic goop would disarm it...if he succeeded.))