Luffy got over that pain remembering that he has other friends too. With us having Shanks' statement who says that it's ok to cry, but one has to look forward. On the other hand, Sabo has inherited Ace' will, people mention that he is much like Ace and when Sabo one shotted Burgess, he mentioned that it seems like Ace didn't forgive him. So Sabo revenging Ace sounds plausible.
Sabo literally said he isn't the one to hold grudges and he went against Burgess because he didn't want to let the same scenario happen ever again (Losing a brother).
Sabo literally went to Akainu's turf and didn't care one bit about getting to see him or anything like that.
Koala literally said the Marines aren't their enemy, the WG is and he can't pick fights with an Admiral like that.
Yea no, Luffy is beating Akainu, the built up for that was done pre timeskip, Teach and Akainu represents the 2 big villains for Luffy, one pirate and one Marine.
With Luffy being able to block every shit with his Barrier Hakis and has punches so strong it heavily taxes Hybrid Kaido, what are Akainu's options?
As if Oda gives a shit about that kind of stuff, he will just make Akainu stronger than Kaido, quite simple, this is a shonen. You guys overhyped midgame antagonists such as Kaido and BM for no reason. Don't act surprised when Teach/Akainu are revealed to be stronger lol.