Alright so let's talk Tumblr Corrin. This build is all about getting those sweet, sweet triggers, and because we want all those skill triggers, we're gonna need a lot of gold because let's be honest, who wants to grind up all of these skills and do all this optimal talent/mating stuff? Just use My Castle, it's easier. I'd put my My Castle in here where I had most of these skills ready to go but uh, I accidentally overwrote my Revelations file and lost it all, but I'll have it eventually, I promise!

So here's what we need. I recommend having your boon be skill, but this isn't necessary at all, it just helps a bit. ALSO DO NOT MAKE YOUR BANE SPEED OR STRENGTH. Speed is the second most important stat, because if we attack twice, that's two chances to trigger a skill. Strength is also vital due to the base damage it brings. Your boon can be any one of these three, but skill is the most important from my experience. Next we have options.

Hoshidan Unity and Quixotic are a MUST. This gives all skills a base trigger chance of 25%. This is already dumb, but we can do better. Corrin now has 3/5 skill slots left, but that's not enough, so let's give him Nohrian Trust, using up essentially 4/10 potential skill slots. Corrin himself now has 2/5 skill slots, with his partner having a full 5 slots left. For the rest of Corrin's skills, I recommend Lifetaker and Swordfaire. Lifetaker gives guaranteed sustain after every kill, and since we're one-shotting pretty much everything, we're gonna be getting a ton of health back. Alternatively, you can use vantage here instead of Lifetaker. Swordfaire is there due to synergy with a few other skills, plus it covers the weakness of the low chance you won't trigger a skill.

For Corrin's support partner, I recommend Kana, although there's plenty of other options. I just chose Kana due to her ability to use Dragon Fang. These are the skills I've used:

Dragon Fang

Astra

Aether

Luna

Lethality

Other options include rend heaven, which is an excellent choice, Sol, especially if you forgo Lifetaker, Vengeance if you typically find yourself low on health due to removing healing skills. If you do use Vengeance, Vantage is highly recommended.