Use of Kyogre

Water is a great offensive type, is just that current raid bosses aren’t weak to water, when Claydol was Kyogre was its best counter by a large margin, we can only wait for a relevant raid boss weak to water (cause Claydol isn’t relevant in the meta)
Also the special move of Kyogre, Origin Pulse is on the data of the game and it’s on par with Precipite Blades the best charge moves in the game thanks to good base power, being multi bar and have low cooldown, however they likely only will get it when mega evolutions are implemented on the game

If Ho-Oh is the next raid boss, with a buffed fire move (rumored), then Kyogre will be a good counter, just behind Golem and B/SE Tyranitar.

Other than that, Kyogre is strong enough to be considered a generalist, except against things that resist water. Good for taking down anything that is weak to water (Tyranitar, Fire, Ground, Rock), and may be effective against some of the Regis too.

That said, trying to predict the next Legendary is a guessing game, and given that there are some things Kyogre is effective against, it's good to have one ready to go, maybe more.

Kyogre is great for mons like Ho-Oh - despite not having double effectiveness like Golem, Waterfall is slow and hard-hitting, which is good against its massive defense stat.

It's also a great generalist, especially in the rain. Water is a type that doesn't have a ton of use right now but it is effective against a TON of types overall.

Remind me to candy my maxed out kyogre.

Seriously, he is not best at anything, at present, but a pretty good option for a lot of uses.

Kyogre with blizzard is good for Hydro Pump Lugia, where Tyranitar is almost useless. Unless you have 6 of Raikou/Mewtwo/Zapdos, Kyogre will be of the best of the tank counter, in which the TDO much higher.