Those BlazBlue fans out there will find this trophy very familiar. Essentially it requires you to activate a random item tossed by "Teddie" using his ( Down + O) attack. He has around 11-12 items he likes to toss. Just keep spamming it and eventually you will come across one that causes the poison ailment. The trophy should unlock soon after you pick it up.
*Must be done in arcade mode or online*