Tarrlok was an interesting minor villain to the show. At the start of the series he’s a councilman representing the northern water tribe for Republic City.
He had first tried to make allies out of Avatar Korra, especially as the Equalist Amon was terrorizing the city.
But he decides to reveal his true intentions and use blood bending against Korra.
And he even manages to capture the Avatar.
But surprisingly, it is Amon who finds him and robs him of his bending.
Ironically Amon was actually his brother in secret. They were both sons of the criminal Yakone whose bending abilities were stripped away by Avatar Aang.
After his brother is defeated by Avatar Korra and his whole plan is ruined, they both flee Republic City on a boat. Shockingly, he kills himself and his brother by putting electricity in the gas tank. I didn’t see that coming, but even somebody as morally flawed as Tarrlok realized that even his brother was too wicked for the world.