Drive screws -
The only soft ones I've seen so far were in an old Hardinge Cataract lathe - just brass pins in that case .
Most all I've encountered are pretty hard steel .
A 2 step approach works for me most times :
First, take a nice, sharp flat-ended pin punch, and go all around the screw head, tapping it sideways.
This will usually loosen up the screw in it's bore.
Next, use a Dremel or similar, with one of those little thin diamond cut-off wheels, and cut a slot in the screw head.
Most of the time they'll unscrew right out, counterclockwise .
If it doesn't unscrew, then the previous loosening technique will make it much easier to pry out,
using various other implements of destruction