All you need to do to unlock this trophy is wait until the Anti-Venom suit has been unlocked as part of the story, and then use one of your Anti-Venom abilities to knock out a foe. These are the powers that are tied to the face buttons; you need to hold  and press  to use yur different abilities. The Anti-Venom punch is the most satisfying. Knock a symbiote enemy out and this trophy will unlock.