Rusted screws in outdoor outlet box
Hacksaw?
If you saw thru the rusty plate (twice, one for left slot and one for right) and remove it by pulling it out from under the screw, the remaining screw will be sticking up enough for you to get hold of the whole head with a pliers and unscrew it.
It is hard to argue w Alaska Man (or you) re merits of replacing the whole box.  But it seems like you would need these screws out to do that too.