peoplel remove them in many different ways
if you cant get a decent sized chisel behind it, you can drill a hole in the cast casing behind the bearing shell, to allow the chisel head to get a good lock on it
some grind it out
but, if theyre that bad… is your dum shaft ok?
there is only one answer, and that is brute force and determination, it will come out, you just got to be determined
please work carefully too, protect your eyes, and wear good quality gloves to avoid personal injury