Thaal Sinestro of Korugar used to be one of the most decorated Green Lanterns. Willing to carry out his mission at any cost, he would also be a very snobbish and upheld in his own ego. However, when Hal Jordan became the newest and greatest Green Lantern, this would taint Sinestro's image, making him sloppier in his missions, and even defying the Guardians' orders to fulfill his own needs. Thus, he's exiled from the Green Lantern Corps. But, as he would go into exile, the alien embodiment of fear Parallax gave him a yellow power ring to help him exact revenge on the Corps, thus becoming the single greatest adversary of Green Lantern.

In the Injustice universe, he finds the One-Earth government that Superman and the remaining Justice League members to be very similar to his own government on Korugar. He becomes an ally to the cause, and is one of Superman's greatest enforcers, and a commander to many of the ground forces for the One-Earth government's troops.

Because his lines are all in the Injustice universe, you will only need to emulate Nolan North's performance as Sinestro from the Injustice game (and maybe a little emulation of Mark Strong from the 2011 Green Lantern movie).