Someone with venal motives is corrupt and maybe a little evil. Nobody wants to be thought of as venal.
Venal actions include taking bribes, giving jobs to your friends, and cheating. Venal means about the same thing as "corrupt" or "corruptible." Venal people are considered sleazy and untrustworthy. They're often criminals. No one is perfect, and most of us have venal motives at some point.