How do you defeat Doc. Ock. for the last time?

When he attacks you dodge it and web him. After four go into spidy reflex mode and kick his can.

first off in the abandoned Oscorp building there are 9 switches to turn off. 1 is under the floor and 1 high on the wall. 4 are on the highest platforms while 3 are on the ground level platforms. hitting the one under the floor last is best as usually doc oc will just throw you into the water if you do it first. Make sure you aviod doc ock, the plasma pulse and have have your fnger on the dodge button to avoid the bolt of lightning at all times. after that you will see a cut scene and its now time to fight doc ock, try and get a good distance away from him and as he starts running on his own 2 legs towards you, turn on spider senses and beat the hell outta him. Turn off spider senses and retreat to a safe distance while your spider senses recharge. once they have regained a little do the whole thing again and again and again until he is defeated. Hope this helps!