honestly? stan ezra bridger. him defeating thrawn in rebels? huge repercussions. he basically incapacitated the empire and did the rebellion a huge favour by taking the smartest admiral they had and taking him off darth sidious' little chess board.
imagine if thrawn had been there during the original trilogy. had been in charge of the battle of hoth or endor. the rebellion would not have won that easily, and the empire wouldn't have made the death stars that failed repeatedly. the rebellion would have been going against things like the tie defenders in swr s4.
we could have had a live action marg sabl...
not to mention, ezra straight up just blocked palpatine from getting the 'time travel' card (world between worlds) can you imagine how pissed palpatine was when he did that? when ezra got out of the world between worlds and destroyed the entrance?