My mentee is a slow learner. Rest of the team, both tenured and new team members are very much able to make an impact independently and working together as well. But this mentee of mine, is just not there yet even after being in the team for a little more than 6 months now. As a mentor, what approach I can try, to make my mentee become successful in my team?
First, I recommend my deep-dive on how I was able to grow mentees extremely quickly at Meta. I'm also going to assume that you're an engineer mentoring another engineer.
From there, my advice is split up into 2 broad categories, which I'll separate into 2 different comments.
Some other thoughts:
Lastly, an unfortunate truth is that many low-performers can't be saved. Some might not even deserve to be saved (a lot of low-performers are just jerks and hard to work with). If you feel like you aren't seeing results even after applying all this advice, you should have an honest discussion with your manager about the future of this mentee within your team.
At the end of the day, you need to make sure the team succeeds. Low performers can take others down with them if they suck up too much of your time. Check out this other discussion on evaluating whether you should invest into a struggling teammate.
I once had a mentee (intern) who was an amazing C coder but had trouble with "dev ergonomics" things like UNIX utilities. I tried to help her with the non-core-C tasks so she could maximize her time doing C coding. As Alex said, I would teach her a mental operating model for the non-C tasks and she did become more proficient by the end of her internship. I recognize your situation may be a little different.