Gardevoir

[Seanse]

I think Gardevoir is a pretty good pokemon with a good fairy/psychic moveset but when anyone thinks about a fairy/psychic pokemon only Mr Mime comes in mind tho

My suggestion is just add Calm Mind back on her moveset (passive)
Actually Ralts and Kirlia have calm mind as passive and Gardevoir loses it when evolving.

Don't think it will make her broken since her fairy/psychic rival have 2 strong passives besides a strong moveset.
And if comparing her with another pokemon isnt a valid argument, we can see that she can learn it in all pokemon games by lvling up and by tm learnset (bulbapedia) being almost her signature.
Current moveset:

m1: Psyshock
m2: Future Sight
m3: Play Rough
m4: Imprison
m5: Moon Blast
m6: Pain Split
m7: Draining Kiss
m8: Disarming Voice
m9: Misty Terrain
m10: Psyblast

Suggestion:

p: Calm Mind
m1: Psyshock
m2: Future Sight
m3: Play Rough
m4: Imprison
m5: Moon Blast
m6: Pain Split
m7: Draining Kiss
m8: Disarming Voice
m9: Misty Terrain
m10: Psyblast