Some of these achievements are going to be nearly impossible to do without cooperating from the opposing player. Lighting up a spy while he flicks a cigarette? How often does that happen?
Reflecting a critical rocket and killing the soldier with it?
I read through most of the achievements and they seem like stuff that happens regularly, such as lighting up cloaked spies and lighting up disguised spies. But to have to get every single achievement in order to get the axe is just stupid because it means that in order to get all the unlocks, I'll have to mess up my stats with padded, contrived info and I prefer for my stats to be pure.
Playing medic without attempting to actually get any achievements, I'm currently at 21/39; almost got the kritzkrieg (which doesn't seem that great) but I'm never going to get the ubersaw without "cheating".