While in the body of Peter Parker, Doctor Octopus defeated Black Cat and because of him she lost her secret identity, stolen possessions and her allies. While she was imprisoned she realized that in order to regain all that she had lost, she needed to end the life of the one who took everything from her - Spider-Man.
After she escaped from prison, her first recruit was Electro who at the time was being 'hunted' by Parker Industries to be depowered. She knew that Max Dillon had been more than once humiliated by Spider-Man and she recruited him on her side.
Later on, she continued recruiting people who have had their life ruined by Spider-Man or at least wanted him dead and not on the streets of New York. Notable members of her gang are: Hammerhead and Scorpion and she has an alliance with The Inner Demons and the Goblin Nation.