Gonna get destroyed by all the Mordin fanboys on here, but here goes...

Mordin Solus has the absolute worst character development of any squadmate in the series. In Mass Effect 2, I was actually really impressed by how they designed his character. The scientist who is haunted by decisions from his past, but still understands that he did the right thing for the greater good and that sometimes life doesn't give you clean solutions, you just have to make the best of the options you've got. It's obvious he cares about the world but at the same time has a hard edge and has no problems killing people or doing damage if it'll make the world a better place.

Fast forward to Mass Effect 3... his character is a complete one-sided joke. Somehow he did a complete 180-degree turn on his views towards the genophage for - reasons???? He doesn't even try to explain what changed his mind or how. He's a smart salarian and presumably it must have been something huge to change his mind. I wish the developers had fleshed this out more instead of just resorting to "well, Mordin's a good guy, therefore now he's against the genophage and wants everyone to live in harmony, duh".