!ask when i use yasuo remorseful to a occupied battlefield then a showdown start then i pulled him back to my base using akali legend then send him back again because my akali legend is empowered, how many damage does yasuo deal?

Yasuo's attack trigger deals 6 damage, and the Akali pull-back can't stop or reduce it.

The "When I attack" trigger resolves during the Initial Chain while Yasuo is still at the battlefield. Rogue Assassin's ability is [Action] speed, so it can't be played while that chain is Closed (Reaction only) — the 6 damage happens before you can activate her. Also note the empowered Akali only readies Yasuo; it doesn't send him back to the battlefield.

If you close the first showdown fully (both players pass, combat resolves), then Standard Move the readied Yasuo back in, that's a new combat, so his trigger fires again for another 6 — 12 total from triggers. But returning him mid-showdown won't re-trigger it: "When I attack" is only checked once per combat (Rule 383.4.e.2.a).