Raikou 100%

It depends on your candy and dust levels. Outside of PvP Shadow Ball isn't that useful for him, but if you play PvP it could be a handy second move if you can afford to buy a second move. There aren't many raid bosses where electric is the main need, and its unlikely Kyogre will be out again for a while, but when there's a boss weak to electric he's an excellent counter. His bulk and dps make him a decent generalist too.

I play PvP with a maxed 98% Raikou with two charge moves, and it's a good coverage move that can sometimes catch the opponent off guard. If you have the candy/stardust of course, if not, then wild charge is better.

Raikou is the third best gym attacker (after Machamp and Metagross). If I got a perfect, I would definitely max it out (with WC, not ShB).

A 100% Raikou is absolutely worth spending the resources to add a second charge move, and SB and WC are a great combination.

It might sound a bit crazy, but Thunderbolt is better in PvP than Wild Chrage. Outside of that though, Wild Charge outclasses Thunderbolt in every aspect.

Honestly, apart from the worst legendaries like suicune or the regies, you can max your 95+ and get from a very decent pokemon to a complete beast.
I maxed a 98% latios, knowing that it’s a step behind the other legendary dragons.
But I just love the dragonbreath/dragonclaw combo.