One of the problems with those universal tools for removing stuck fastners is the fact they need a lot of clearance around the part in question. Many cases what I have is in a recessed location or requires removal of another part to get a better grab. This is where the dremel comes out. Once I got lucky and a blob of super glue helped. Im sure if you can weld that might be another ave to go.
PB Blaster also is the best spray for getting stuff loose. It looks like snake oil, but it works.
