Phased plasma rifle in the 40 watt range
Just sayin’........
Heh... the strategic objective is always to get the other side to stop fighting. That is accomplished primarily in three ways; annihilate their armed forces, starve their forces off food, water, ammo, and equipment (in modern warfare, that means knocking out shipping, manufacturing, and transportation), such that they give up, and diplomacy. Any of those approaches can result in regime change for your adversary, which could be a good outcome or a middling/bad outcome.
Combat robots aren't alive, so they don't worry about dying, and that middle option only exists if they can be deprived of their power source; they'll otherwise just keep on coming, and if they run out of ammo, they'll run faster than a human, and arm themselves with whatever's around, including arms seized from combatants on either side.