The Fatman
The Fatman dosn't deny this, in truth, he embraces it! He prides himself on being evil and manipulative. And the most guilble victums of his manipulations? The Undertaker and Paul's own son; Kane. This ability to control the two most uncontrolable atheletes in the WWF only proves that Paul Bearer is the best at his game. His mind games are cruel and he enjoys them to the fullest. He's backstabed his own son, dug up the dead parents of the Undertaker and burned them and has attempted to commit Kane to a mental institution against his will on several occasions.
This is not to mention that he is the cause of Kane's scars. He was the one who ordered the young Undertaker to set fire to their house; killing both of the Undertaker's parents and burning Kane beyond all reconition.
Paul then tricked Taker. He told Taker his brother was dead and made certain Undertaker never found out he was alive until it suited Paul Bearer's purposes.
This man is cruel, heartless and unforgiving. Crossing him could spark the begining of a grudge that he would never let go of.