The hosts were stunned 2-0 by the Super Eagles in the final group game but they recovered on time to defeat Niger 2-0 in the semi-finals to set up another meeting with Nigeria.
Appiah, who is expected to be in the stands to scout for players to the main national team, believes his assistant Maxwell Konadu will take his revenge.
“I strongly believed before the tournament that the Black Stars were good enough to contest for the title. All they needed was motivation [because they were eliminated from the Chan tournament],” Appiah told Angel FM.
“As usual of Ghana, we always don't start tournaments on a good note but we end well, so what the team needs now is our support and prayers so they can win on Sunday. We have the potential to defeat Nigeria despite losing to them in the group stages so, we will revenge,'' he added.
Nigeria are the only side yet to taste a defeat or concede a goal in the competition after five games played.
The winner will take home $100,000 as cash prize while the finalists will pocket $50,000.
Niger and Benin will face-off against each other in the third-place match earlier on Sunday.
Fox Sports holds exclusive rights to the 2017 Wafu Cup of Nations.