Stallbreakers that Usually Work:

SD Marowak-Alola
Taunt + NEN Gengar
SD AOP Kartana
Taunt Serperior
Zygarde
SD + 3 attacks Landorus-Therian
Taunt Tornadus-T
CM Psychium Latios
Mega Heracross
SD Mawile
Shed Shell Tapu Lele
SD + Taunt Bulu
CM + Flash Cannon Reuniclus
Gigavolt Tapu Koko
Sub Heatran
NP + Taunt Thundurus
Waterium Z Manaphy
NP Togekiss
Rain Dance Araquanid
Taunt Mega Gyarados
Mega Garchomp
SD Fire Fang Garchomp
Electrium Z Necrozma