Pokemon Violet - 7* Delphox the Unrivaled
1After Chesnaught's rerun was postponed for a month due to glitched paradox drop tables, we've finally moved on to the next 7*! And it's a nice breather.
Delphox has hidden ability Magician, but it does nothing in raids so don't worry about losing your item. She (yes, for once the event raid boss is guaranteed female!) starts off with a mere Dazzling Gleam at the start, and then has the very straightforward moveset Fire Blast/Psychic/Dazzling Gleam/Will-O-Wisp. 157 seconds in, Delphox resets her debuffs; 225 seconds in, Delphox uses (newly-available!) Nasty Plot. Meanwhile, at 85% Delphox drains one tera charge, and at 60% she resets your buffs/negates your ability for one turn, and also uses the fun move Magic Room (items have no effect for five turns). Finally, the shield goes up either after 67 seconds or at 87%. (It's also worth noting that this 7* raid only lasts 7.5 minutes like 6* raids, instead of the usual 10 minutes.)
Delphox only has special attacks, and normally has noticeably lower physical defense than special defense thus encouraging physical attackers... if it weren't for will-o-wisp. As a result, unless you're immune to burn (either through fire type, or abilities like Flash Fire or Guts), you probably want to run a special attacker.
0:00 - Support Armarouge
As it turns out, fire/psychic/fairy is pretty thorough coverage! The only things that resist all three are Armarouge, Delphox itself, and Flash Fire Heatran. Heatran itself is pretty good offense-wise (it can use Iron Head if you want to focus on physical damage or just Flash Cannon/Steel Beam otherwise, and also has Metal Sound) but of course it's transfer-only and can't be bred (and anything transferred always has its tera type be its main type, so if you want tera steel then you need to spend 50 steel shards).
Meanwhile, Armorouge and Delphox are more suited for support roles: both can use Mystical Fire (-1 SpA) to help ally survival, and have Calm Mind (and/or Nasty Plot) if they also want to eventually attack. Armorouge has an edge in pure support, though: Acid Spray's -2 SpD is of course incredibly useful.
Armarouge is able to solo with an incredibly slow but safe strategy: use Calm Mind 6 times, then Flash Cannon (put up shield, also get a tera charge), then use Acid Spray 3 times, and finally tera psychic Stored Power. Of course, if you're using Stored Power, then another Pokemon comes to mind...
5:30 - Solo Galarian Slowking
More specially-bulky but lacking a fire resistance (and burn immunity), Slowbro/-king are the traditional Stored Power oneshotters! Regular Slowking is neutral to fairy whereas Galarian Slowking is neutral to fire (and psychic), but you're bulky enough that it doesn't change much. Access to Nasty Plot + Acid Spray is very nice, but in the end +12 Stored Power's 260 base power is still better than super-effective Sludge Bomb's 90x2 (and you'd need to use tera shards to get tera poison anyways, since G-Slowpoke is mono-psychic).
...Well, having written all that and comparing them, the Armorouge strat is probably better... Armorouge has 125 SpA and burn immunity, whereas G-Slowking has 110 SpA but far better bulk. Gotta show off the random shiny, though!...
Oh, one last strat which I heard of and thought was amusing but couldn't do myself since I don't own Legends: Ursaluna can do Belly Drum, then attack cheer, then Facade/Giga Impact, for a super-quick oneshot... if you're also willing to gamble on getting AI Arcanine, then having it Leer twice, while also having Delphox miss/not oneshot you with Fire Blast (but still burn you for Guts, since you need to hold a Normal Gem/Life Orb for damage). Ursaring has far worse bulk so it definitely couldn't pull it off after a bunch of attempts (Delphox never bothered with Will-O-Wisp and instead used Psychic/Dazzling Gleam for their 100%-accuracy after I used Belly Drum).