Send a new transaction to accelerate the targeted unconfirmed transaction either by using Child-Pays-For-Parent (CPFP) or Replace-By-Fee (RBF).

Background:

1. In Bitcoin, a transaction can only be included in a block when all its inputs are confirmed. This requirement can be used to increase the effective fee rate of a stuck low-fee transaction. One of the stuck transaction's outputs is spent in a child transaction with a much higher fee. Miners include the transactions with the highest fees first to maximize their revenue, but the high-fee child transaction can only be included once the parent transaction is confirmed. The miners are therefore incentivized to include both the parent and the child transaction together in a block. A Child-Pays-For-Parent transaction can be created by a recipient of the transaction or by the sender if the target transaction has a change output.
2. In Bitcoin, a transaction can be replaced by a new transaction with a higher fee as long as the new transaction spends few or all of the same inputs used by the original transaction that's being replaced. Unlike CPFP, only the sender of the transaction can create a Replace-By-Fee transaction, and only either of the transactions can be confirmed. More often than not, the replacement transaction with the higher fee will be accepted by the miners.

Notes:

1. As other coins do not have a blockspace market, this route is only available for Bitcoin at this time.
   
2. Using CPFP, if a target transaction depends on other unconfirmed transactions, this route also adds sufficient fees to elevate the entire transaction ancestry's effective fee rate to the cpfpFeeRate.