The Atom(Ray Palmer) vs Ant-man (Hank Pym)
Ray Palmer and Hank Pym are two of the greatest minds in their respective universes, and great minds think alike- they’ve both invented a means to shrink down to microscopic size while retaining their original weight and strength levels.
Ray Palmer also incorporated a means to shift his mass to any part of his body, like his fists, giving him concrete shattering punches.
Hank Pym, on the other hand, delved deeper into the science of size shifting and invented a serum to allow himself to grow rapidly to giant size that also comes with giant strength. He also wears gauntlets that emit electric blasts powerful enough to stun an even kill.
Although they both prefer to study in the laboratory or teach in the classroom rather than be in battle with their teams, these two are more than capable combatants, but against each other? It’s hard to say.
Hank can’t smash Ray, because the Atom could easily evade a giant by shrinking down, and Hank could easily evade attacks this way as well. At a distance, I suppose Pym has the advantage with his Stinger gauntlets, and up close, Atom has the advantage with his bone-shattering punches, but there are too many factors to say for sure. I’m gonna have to give Ant-man the slight edge due to his more lethal standard equipment, but it’s a close one for sure.