Great League Gardevoir counter

Lairon, Melmetal, Skarmory and Steelix.

anything thats part steel. Sableye might do well too, caps out right under 1500, and also hits medicham for SE damage as well if you see those.

Ive heard a lot of negative things about gardevoir in pvp at least upper leagues.

Anything with higher TDO, and gardevoir scores pretty bad in overal TDO, so literally anything with higher TDO. This includes, but is not limited to: Meganium, Venusaur, Tropius, Torkoal, Blastoise, Steelix, Alolan Marowak, Lanturn, I could go on and on. Honestly there are alot of counters because Gardevoir just sucks in the Great League.

Gardevoir has pretty terrible bulk in the great league, so (as others mentioned) anything that can at least hit it for neutral damage and not take SE damage back should do just fine. Fighting-types really don't like her, so for sure don't bring those.