it doesn’t get much damage tbh, u2 adds a bit more but your usually going to use 2 rekkas for a hit confirm, the red focus adds another 2 levels of scaling, i beleive ultra in a combo adds another level of scalling, and your going to get a nudered ultra. U1 is a great anti air, it gets great damage from a dp fadc, dp whiffs, focus crumple backdash etc. it gives you good positioning afterwards to land a meaty lp fireball from midscreen and a meaty hp in the corner for continued pressure.
cr.mk xx rekka, rekka xx RFC, ultra 1
390 damage 250 stun, 3 bars, full ultra
cr.mk xx rekka rekka xx RFC, ultra 2
408 damage, 250 stun, 3 bars, full ultra
cr.mk xx rekka rekka xx RFC, cl.hk xx hp rekka rekka rekka
306 damage, 400 stun, 3 bars
cr.mk xx rekka rekka xx fadc cr.lp, st.hp xx ex LMT
331 damage, 400 stun, 3 bars
cr.mk xx rekka rekka xx super
410 damage, 200 stun
heres a set up.
back throw (140 damage, 150 stun), j.lk, cr.lp, st.lk, st.mk xx mp rekka, rekka xx RFC Ultra 2 (280 damage, 295 stun)
so you get about 420 damage, 450 stun if everything goes to plan, with 3 bars and a full stocked ultra 2
that doesn’t take into account low health scaling either, and your j.lk has to hit, it could get blocked, and say on someone like cammy which the back throw, j.lk set up works godlike on, if she does dp, she flies away, with U1 you can option select it with the j.lk to get her from full screen if she does dp.