Where can i report an Admin for abuse?

Depends on the nature of that report:

1. If it has something to do with GameTracker.com (note GameTracker Administrates NO game servers), use the report button on the profile, server blog post, forum post, etc. and describe the issue in the input box.

2. If you have a complaint for a server admin on *some random server*, you need to contact them, not GameTracker. You may be able to find information on contacting them on their server page, but if not, we cannot help you further. Google would be your friend in that case.