Why hesitate?

With the assistance of Peter and the Hello Kitty ghost, the over 20,000 ghost members quickly surrendered to Alexander. 

Alexander treated these surrendered ghosts generously. Unless they were particularly malicious, he allowed them all to join the ranks of the Fierce Ghost Association, including even Soren. 

Although Soren had a somewhat feminine demeanor and wasn't adept at combat, he had a large number of mature female fans. Right now, what Alexander needed most was numbers, not power. 

Only with significant numbers could they trigger the bandwagon effect amongst their enemies.

The Fierce Ghost Association was now a major force, soon to control an entire block, and they needed to entertain their many members.