Pleaselog inorregisterto add a comment.
I’m unsure whether or not you’re talking about Mega Gardevoir or normal Gardevoir. I’ll assume the former.
Steel-types:though it often carries Will-O-Wisp and Focus Blast, a lot of good Steel-types can counter it should they switch in freely, like Mega Scizor, Mega Metagross, etc.Faster Poison-types:while Psyshock easily OHKOes the lot of them, faster Poison-type Pokemon like Mega Beedrill & Gengar force it out easily and can inflict massive damage on the switch-in. Mega Beedrill, in particular, can collect momentum with U-turn upon a forced switch.Faster physical attackers:as its Physical Defense is so low, many faster physical attackers can easily bring it down. Mega Gardevoir variants lacking Will-O-Wisp are countered by bulkier, slower attackers, too, that can take a hit from it.
Source:http://www.smogon.com/dex/xy/pokemon/gardevoir/
Hope I helped!