This one is pretty hard, especially considering that Gliscor is most often seen on stall teams. This leaves a few options that can deal with or at lest pressure Gliscor's common partners in crime. Cloyster has a hard time with Toxapex and Mega Slowbro, but it's a great mon overall. That Aegi set is nice, but once the ballon pops, Gliscor can muscle through it. Avalugg loses to SubProtect spam if poisoned. Mamoswine is great, especially if you can hit Fissure on a switch-in, but it struggles against Skarmory. Skarmory is a strange one. Gliscor can't touch it, but Skarmory itself can't touch it back. Mega Sableye is also pretty good, even though it's only seen on stall teams. That Ttar loses to Toxapex. Not a fan of it. Glalie requires too much skill to use, but it's a solid option. Greninja is shaky. It has the tools, but Chansey/Blissey and LO recoil wear it down quickly. Donphan is a nice underdog option here, but loses to Skarmory and Mega Slowbro/Venusaur. That Salamence struggles against Skarmory and Mega Slowbro. Alas, no one nominated Sub/Taunt DD Mega Gyarados, so I guess I'm going with can't say's Mamoswine, since it's easier to fit on a team compared to Glalie, Skarmory and Mega Sableye.