How to Turn Kaidan Renegade

If you want to turn Kaidan "renegade" (make him xenophobic) in the first Mass Effect game, you must play as female Shepard. The reason being is that he can only be turned renegade during the romance path.

Romancing Kaidan is pretty simple. Talk to him after completing every main mission. Be kind to him, and be sure to tell him you're interested in him. If the topic of Liara comes up, do not tell him that you're romantically interested in her.

Also, keep in mind that you will need 5 points in charm or intimidate to ultimately be able to turn Kaidan.

Kaidan will eventually give a conversation which reveals that he killed Vyrnnus at Jump Zero. In this conversation, he will say, "So yeah, I hated that turian. But he wasn't a turian to me. He was Vrynnus." You need to respond to this with the "turians are all the same" (bottom right) dialog option. On the following dialog wheel, you want to pick "I'm not so sure" (bottom right). Picking these two bottom right options should open up charm and intimidate options (left side). You can pick either of these charm or intimidate options to successfully turn Kaidan renegade.

After completing another main mission, Kaidan will have a new conversation, and he should express an anti-alien view. Encourage him by picking bottom right dialog options. Do not pick any charm or intimidate options in this conversation if you see them because these will only undo the changes in Kaidan. 

You will know that you've successfully changed Kaidan when he rants about those "damned aliens" before the love cut scene.