We tend to use "whatsoever" to add emphasis to the end of a negative statement. For example: There is no problem whatsoever. That makes no sense whatsoever. You could replace "whatsoever" with "at all" in these phrases, and the meaning would be the same. "Whatever" is a conjunction meaning "anything or everything that". It's often followed by a noun+verb phrase. For example: I'll do whatever you want. He agrees with whatever she says.