Basic and Armored Solidiers
Basic Soldiers are easy to take out and don’t pose much of a threat, even when in groups. Simple cover will keep you out of harms way as they rely primarily on pistols and SMGs. A single headshot will take one of these guys out.
Wasting any of your abilities on them isn’t necessary unless you find yourself off-guard. If that ever happens, your Time Shield (unlocked during Act One) will be very helpful. It pushes back weaker enemies, protects you, and slows down time a bit around you allowing you to line up perfect shots.
Armored Soldiers (we’re talking vests and helmets) are pretty much the same, though they take a bit more damage than their unarmored counterparts. They aren’t much of a reason to panic, so breathe easy.
Time Stop, the first power you unlock (not counting Time Vision), is also useful for just holding a few soldiers in place so you can either light them up or find cover.