An autonomous vehicle, flying at 1-2 metres, very fast, hardly targetable and carrying either a small bomb or a device which projects shrapnel precisely at an individual soldier.
At present machines like this would be expensive and limited in range-- you'd probably need a big GPU on it, you'd probably need some kind primary cell that outperforms rechargeable lithium-ion batteries, maybe split it in two half-- one attacking part and one slow gliding part. Thousands of dollars, and weight, complexity, etc. But I am fairly convinced that machines like this are possible and I don't see how human front-line soldiers can operate in an environment saturated with them. I don't even believe that long-range assaults, 1000 km etc., are something these kinds of things won't be able to do-- after all, many birds migrate vast distances, and I think aluminium contains more energy than fat per weight.