[someone banned me from my server]

OK, I disabled command blocks, and also went into the files section, and manually removed them from the ops file, and myself from the banned file. 

Now I have access to the world. Sadly they just filled it with destructive stuff, but I can rebuild it.

Thank you all for your help!

[someone banned me from my server]

someone asked to get op in order to help me build new things. 

After a couple of hours he gave op to his friend, and after that they just banned me, and ran a command that kills me every time I try to get back in.

Is there anything I can do to regain access, or the only thing is to delete the server?