Finally got it. After losing again to #49 today, and than next time got to 59. Seems, The Miz at the last opponent is my doom or something. Bastard.
At #20, I started using finishers. Would have 3 saved up, and used one, than when I could would pin them, and by than had a Signature. Used that on next guy, kept going till pinned them. So, would usually have 2 or 3 finishers. Kept going with the running DDT thing. Knowing how to counter definitely helps.
#40-50, I ran and did a DDT, than when they got up, hit a finisher. So to weaken them, and kept going till a pin. Sometimes lucked out, and would hit a finisher and they'd be K.O.ed
Glad at #50, that it was Sin Cara, and had 2 finishers stored. Hit a running DDT, and 2 finishers to be sure it was done. Pinned him, and got the damn thing finally.
Took me at least 15-20 tries over the course of the days, for this thing.
Good luck to others, keep at it.