Agnin

Mass Effect 2
A hothouse planet, Agnin's scorching clouds of methane and sulfur dioxide give the planet a pale green color in visible light. The SO2 from volcanic activity rains down as sulfuric acid in the upper atmosphere, but this is boiled away before the liquid ever reaches the surface. Agnin's harsh environment has prevented exploitation by anything except probes.

Mass Effect 3
A hothouse planet, Agnin's scorching clouds of methane and sulfur dioxide give the planet a pale green color in visible light. The SO2 from volcanic activity rains down as sulfuric acid in the upper atmosphere, but this is boiled away before the liquid reaches the surface. Agnin's harsh environment has prevented exploitation by anything except probes.