1st Encounter: Attack him with attacks dodging when needed (mostly jumping up from his shock waves in the middle). When he perches, use the to knock him down on whatever he is on. Attack him in the middle when you see oppurtunity, and don't forget about rage () to make this go by a lot faster.
2nd Encounter: You'll have to wait until Electro drops his shield to attack. When he starts gaining life from the generators, jump and press to stop him. Repeat these two steps until you take all of his life out.
Final Encounter: Electro will be a giant now. Wait until one of his hands rests near you and go use the prompt. After a few times you will have to use flying debris to get to the other side where Electro is facing. From here it's more survival, as you avoid his fist attacks as well as the enemies he conjures. After his health is low enough you can use the prompt to finish him.