In your opinion, what is the biggest factor that makes Ikemefuna accept the fact that he is not returning to his homeland?

The fact that Okonkwo stands over him, making him eat his yams proves that Ikemefuna is not going home. He has to eat to survive in Umuofia and has to accept Okonkwo as his leader. Once Ikemefuna sees the resolve and fierceness of Okonkwo, he accepts his fate and actually becomes a part of Okonkwo's family, overcoming his fear and homesickness.