Tekken is quite doable although it can be tough to keep up with a really good opponent. There's not a lot of stereo sound if any, but there is a certain ...rhythm ...to it, if you play it a lot you can kinda get a feel for it.

As for an accessible fighter, first thought I had was Skullgirls, which on Windows at least even has screenreader narration in the menus

Easy to learn, hard to master would be Killer Instinct. The fluidity of the game plus its two-way interaction nature, compared to the singular equivalent of games like Mortal Kombat 9/x/11 or Street Fighter definitely raises it in my book, plus the soundtrack and sound design and the fact it goes on sale fairly often too. Xbox One, PC and Steam versions are available.

Happy to discuss if you have questions.

I'm one of the volunteers with www.everyone-games.com if you'd like to lead a workshop at our event in October, teaching others how to play fighting games, that would be a brilliant addition to the event

I just got Ultimate Marvel Vs Capcom from the Humble Bundle. I really enjoy it. Mortal Kombat 11 and the Injustice series may also work. You may want to avoid games like SoulCalibur and Tekken with have more than just left/right movement.