When knocking off another player by jumping down, it helps to land and aim at them from behind or to the side. If they see you, they’ll probably be ready for you to jump and hit them right in front of where they’re looking, rather than from behind. Generally with this strategy they’ll be falling before they can hit you back
On Bedrock, small blocks such as carpets and pressure plates can be useful since a block can be placed at the front of said block/item (by using the forward block placement that’s commonly used for bridging). You stand on top of the pressure plate and place a block in front of you, and the placed block will be 1 block higher than if you weren’t standing on a pressure plate. This can be an efficient way to go up and forward at the same time, especially if you have limited blocks. The method works with a lot of non-full blocks; it can be done with coral for example, and it can even be done with candles if you stand exactly in the middle on top of the candle.
Similar to that, a block can also be placed on the top edge of a banner that’s on the front of the block you’re standing on, but you also have to stand in the exact middle of the block; I don’t know if this works on Java or not
Lastly, if you place down a carpet and you have an extra one on you, you can stack the carpets
