It is frustrating fighting against players that have high ping, It's much harder to use PvP techniques like strafing and w tapping against those players. They get delayed knockback and if they have really bad ping then they start teleporting which makes them even harder to fight against. But lag isn't really an advantage either, just like how the lagger gets delayed knockback it can also work against the lagger, the high ping also makes it harder for the lagger to land hits on the other player. You can't really blame the player who is lagging of course, not everyone has the best internet connection and not everyone lives on the same part of the world, they can't really overcome high ping due to geographical distance either.
The best option for you would be to simply just report the player accusing the lagger of cheating to a staff member.
