Support
Support runs inside the app, because a ticket raised there already knows which account, match and tournament you are asking about.
Raise a ticket
Open KickHeroes, go to Profile, then Help and support. Raise a ticket and replies come back in the same place. You do not need an email address.
Delete your account
Profile, then Settings, then Delete account. Deleting removes your profile, your stats and your place on the leaderboard.
Leaderboard
You are only on the global leaderboard with your say-so, and there is a switch in Settings either way. Turning it off takes effect the next time the board loads.