Lars was formerly a huge jerk most of the time. In an effort to appear cool and uncaring, and to hide his low self-esteem, he pushed everyone who tries to help him away. He secretly cared more than he lets on, especially about Sadie, but was embarrassed to be seen with her because it broke down his indifferent facade. When he was revived by Steven on Homeworld, his real personality was able to shine through, away from the stress of his Beach City social life. As Captain Lars, he is a determined and passionate leader for the Off Colors.

Voice reference: https://www.youtube.com/watch?v=kEly_Gz2ONU (skip to the end for Captain Lars)