Aiwei is a jerk and all that, there's no denying that, but his bending skills are underrated. He is the only person other than the GREATEST EARTHBENDER of all time, Toph Beifong who literally INVENTED metalbending that is a human lie detector! He was also able to raise a solid chunk of metal fast enough to block korra's firebending.

Unrelated to his bending skills, he is an excellent liar, who was able to convincingly lie to everyone about who betrayed Suyin and let The Red Lotus into Zhaofu.

He was also able to claw his way to power within The Metal Clan government.