CORNBRINGER
If the MC ever encounters Aang and his group again a possible reason for why he refused and continues to not teach him his style of water being would be: 1. Their personalities clash. 2. The peak/core of each bending style requires the bender's state of mind and emotions to be in harmony with the respective element. The Avatar must master all 4 elements and thus must learn to be in harmony with each/all of them while in a state of balance. The MC has polished his water bending and specialization to an extreme point, and continues to do so. Even a cursory glimpse into his style and training will be enough to convey his passion and love for the art of water bending and may influence the Avatar's emotional state and mindset to favor the 'push and pull' state of water bending too much and thus make it difficult for him to get into the proper state of mind to harmonize with the other elements.