you can remove all transactions from your own mempool by stopping core, deleting the mempool db, and starting your wallet with -zapwallettxes, but that's just from your own mempool. AFAIK, the gui has a feature to "abandon transaction", but that's more or less the same (it differs on a couple things on a deeper level, for example iirc abandoning only works after the tx is no longer in your own mempool so it clears the tx from your wallet not your mempool) . Once a valid transaction has been broadcasted, it'll be stored in the mempool of most of the other nodes of the network, nodes you have no controll over whatsoever.

There is no way of "deleting" a transaction from other node's mempools, the only way it'll get cleared from other node's mempool is if your transaction is included into a valid block, or if the node itself decides to remove the transaction (usually because the mempool is over a certain size, or if the transaction remained unconfirmed for a certain amount of time).

I would discourage to abandon or zap unless you have a very good understanding of what you're doing... Eventough you no longer have a record of an unconfirmed transaction that has been abandoned, it might still be available in the mempool of a mining node, so a miner might still use this transaction in his/her block. You might end up paying somebody twice, or you might end up double spending an unconfirmed output, and the receiver might brand you as a "scammer" as a result (eventough you had no intention to scam)