KUCHINAWA
While he was once Sheena's friend growing up in Mizuho, he kept a grudge hidden deep inside of when Sheena failed with Volt. He and his brother Orochi's parents were killed during the accident. But, he not only bears her a grudge for that, but when she endangers Mizuho for failing to kill Colette. He's overly bitter, at first appearing as her old-friend, then tries to kill her a few times during the game. He steals Corrine's bell, forcing Sheena to fight with him, and leaves the village afterwards. If you're victorious, he starts to try and think differently, promising to keep close watch over Sheena to make sure she upholds her duties and promises.
Sheena is at first happy to see Kuchinawa when you meet him, but it soon turns to worry and then sorrow as he betrays Mizuho and tries to kill her. She's hurt that her once friend feels this way about her, and even offers her life to try and make things better and save the party. Zelos is the one who pulls Sheena way from sacrificing herself to Kuchinawa, and helps her try and organize her thoughts afterwards.
There you are good sir