I laugh at my athiest coworker.
Do they know you make fun of them?
Yes, they know. Their fault is that they're really bad at what they do.
It does not look good to treat your atheist coworker poorly. People will think you are being a bully. You should treat everyone the same regardless of their beliefs.
I just want to bring the lord to their knees and I don't like the atheist.
But it's not right to mock them just because they don't believe in God like you do. You should treat them with more respect.