1000 Gholdengo

Hex is preferred over Astonish for its higher energy generation to fuel Gholdengo's expensive Charged Attacks. Astonish is also simply awful.

Shadow Ball is Gholdengo's bread and butter STAB attack, being its cheapest Charged Attack and having solid DPE. Focus Blast is extremely expensive, but it has great DPE and offers nigh unresisted damage when combined with Shadow Ball. Dazzling Gleam's coverage also pairs well with Shadow Ball, but it has less DPE and doesn't have as wide of a coverage as Focus Blast does.

Although Gholdengo's amazing typing grants it a wonderful set of resistances, its frailty and lack of cheap Charged Attacks severely dampens its potential. Hex is also a pretty mediocre Fast Attack. It can be a nuisance to the Bastiodon + Medicham core, though.

Gholdengo is a bit bulkier in the Ultra League and can fire of its attacks a bit more consistently, although it's still not great. It picks up key wins against several top meta threats such as Cresselia and Cobalion, but it's not something that most other Ghost-type Pokemon can't do anyways.

It can harass the common Zacian + Dialga, which at least gives it a niche. Gholdengo's stats aren't particularly amazing, but they aren't awful either. It is bulky enough to make use of its resistances, although it is far from being great at abusing them. Gholdengo is stronger in Premier formats, where its stats can shine better, and it won't have to compete with Giratina-O for the role of a strong Ghost-type Pokemon.