RBF can be used only by the sender.
Thank you, I gain from you very well. Like he his using wallet like electrum in which he can be able to spend unconfirmed transaction, he can just generate a new address and use higher fee for the transaction into his new address on the same electrum wallet. That means the transaction will be confirmed very fast if high fee is used.
That's called CPFP (Child pay for the parent) and is different from RBF.
If a transaction has been marked as RBF, you can replace the unconfirmed transaction with a new one paying a higher fee. For creating a new transaction that can replace the first one, you need to have control over one of inputs.