I think that Tyler actually liked Wednesday. He was willing to help her escape Nevermore, which would have gone contrary to Laurel’s goals. He refrained from going all out on Eugene, only injured him, because he was Wednesday’s friend. Likewise, he abstained from hurting Enid when they were exploring the Gates house even though he easily could have followed them outside of the house, once again because she was Wednesday’s friend.

I think he only turned on Wednesday after she locked him up and wanted to experiment on him. It was then that he realized that despite her cold exterior, Wednesday wasn’t like him and wouldn’t accept his actions.

Of course, he would have turned her into Laurel all along because she was his master, but I think his feelings complicated things and he wasn’t just stringing Wednesday along.