Originally, the Black Swan had the power to infect the minds of others with a telepathic "virus" (akin to a computer virus) capable of disrupting neural functions to varying degrees. He was also able to use this ability to search others' memories for information and heal certain types of psychological disorders, as he did for the mentally ill man named Ratbag. He was also a highly skilled fighter and assassin.
He proved able to absorb not only knowledge and skills, but also physical powers from others in a moment of great stress.
After absorbing part of Deadpool's abilities and memories, he had a healing factor, but his telepathic abilities were diminished. Upon absorbing the powers of both Deadpool and Agent X, his healing factor and telepathy were both increased to a great degree. He was also able to levitate himself at this time.