You decide to destroy a base containing vital research that includes a cure for the Genophage - a genetically engineered disease designed to stop the Krogan taking over the galaxy. Wrex, your Krogan ally disagrees violently. With Wrex at your mercy, you decide to spare his life.
"Before I could convince him to stop... he ran, leaving me just second to extract my squadmates. I tried... but I wasn't fast enough. I could only save one of them."