What did Tyrion actually do for Daenarys?

Hi, I just finished rewatching GOT, but I don't remember good things Tyrion did for Daenarys as her Hand. I might be very stupid but most of the things that seem good at first backfired at Daenarys. He negotiated peace with the slaver who came soon anyway and almost destroyed Mereen. Then his war strategy lost Daenarys the Reach (This also gave Cersei enough gold to repay the Iron Bank), Dorne and the possibility of retaking Iron Islands. And last his truce with Cersei just ended up giving her time to prepare for the war. Only good thing I remember is his use of red priestesses, but that could backfire too if given time. And I know he made Daenarys give mercy many times, but that didn't end up well either. Please tell me where I am strong.