Online bullying is a part of cyber crime.
You can try to avoid them as much as possible. Don’t let those trolls get into your head. The best way to deal with them is not to respond. People on online media don’t even know you personally. It’s easy for them to attack you, but you must remain unbothered. If you will react, it will entertain them.
Or else, you can delete the mean comments. Now, most of the online platforms have a disappearing mean comment feature. You can just apply that. This will restrict the appearance of mean comments. Some apps also help to delete the mean comments permanently.
You can also block or report the person bullying you.
Further, if you feel that the above steps aren’t sufficient then you can anytime file a complaint under the cyber crime. You can either report them on the same site of bullying. Or you can contact to any site handling cyber crimes.