I've worked with people like this, and it's very tough indeed. My Advice is to not get emotionally invested in it; you can be the best coder you can be and set

I've worked with people like this, and it's very tough indeed. My Advice is to not get emotionally invested in it; you can be the best coder you can be and set an example, but you can't make someone care who doesn't. If he's just unsure, branch off his work and show him a diff of what he's not doing that he could. You can beat the drum and push for better, but if you push too hard or nag you'll meet more resistance. There are many cases where I've made a case for something, had it shot down, only to see the same or similar being decided as the direction a few months down the line. But really, just let it go emotionally. If he's writing code that is problematic and his boss doesn't care, then you shouldn't care. Then again, you are the technical lead. So, who is responsible when something goes wrong? who's head is on the chopping block? because that's the person that gets to make the call. If that's you, put your weight into it and do not let up. if that's your client, advocate for best practices, but accept that some people need to go their own way.