Gliscor

Great League: 2 / 5

Gliscor is a very interesting Pokemon in PvP, and a difficult one to use. A high Defense stat gives it good bulk, while its Flying/Ground typing causes it to only have two weaknesses (including a double weakness to Ice). Gliscor's moveset isn't anything too spectacular, but access to the powerful Earthquake makes it valuable against Steel tanks. The struggle of navigating around ubiquitous Water Pokemon is, however, a major issue for the flying scorpion, which often has to shield bait with its cheaper charged moves to land Earthquake, reiterating the difficulty surrounding its use. Overall an underused pick that can definitely catch opponents by surprise, but not without major drawbacks limiting its overall performance. 

Ultra League: 3 / 5

Gliscor has its perks in Ultra League, threatening Steel-types with Earthquake and dealing damage to Giratina with Night Slash. Unfortunately its moveset isn't strong enough to brute force its way through many neutral matchups. Ice-types including the popular Lapras are also Pokemon that Gliscor must avoid, and Togekiss notably walls it completely. While it can still do well, more popular meta picks tend to do it without being as picky about their matchups. 

Master League: 0 / 5

With a max CP of 2692, Gliscor lacks sufficient stats to perform well in Master League. However, the key coverage mentioned above impressively makes it a viable option here too.