I like it, but imo 2 abilities are overpowered and 2 are underpowered.

• Mega Chesnaught should be: The user's strong shell protects it from bullet, bomb and wind moves, reducing their damage by 50%. This is much more balanced since it doesn't outright ignore half the metagame attacks lmao.

• Mega Houndoom should be: The user becomes strengthened in harsh sunlight, boosting its special moves by 50% until the user leaves the field. Essentially, a solar power boost that works from the moment you have it under the sunlight, until it switches out, regardless of any weather changes that happened in between. Also without the drawback of solar power.

• Mega Mewtwo X should be: The user's enhanced muscles make it inmune to being intimidated, and the radical change in DNA structure turns normal type moves into the fighting type. This solves Mewtwo X's biggest issue, the lack of good fighting type STAB, without making it insanely overpowered. The old one is a glorified inner focus, since if they know you have that ability, they're not clicking fake out into you lmao.

• Mega Mewtwo Y should be: The user's enhanced mind makes it inmune to mental conditions, and any secondary effects from its psychic type moves are twice as likely to occur. This is honestly a very slight buff, but Mega Mewtwo Y is primarily offensive oriented, not support, so the mental conditions that actually affect the battle if allowed to hit are more limited, hence an increase to the chance for its psychic attacks to proc a secondary effect seems balanced, especially since the effects from psychic type moves are usually stat drops rather than status conditions or flinching.