The incorrectly spelled word is:

☀ Acquaintence

The correct spelling is "Acquaintance." It refers to a person known to one, but not a close friend.

Explanation of the other options:

☀ Abandon: This word is spelled correctly. It means to leave or give up completely.

☀ Alliance: This word is spelled correctly. It refers to a formal agreement or partnership between individuals, groups, or nations.

☀ Acquisition: This word is spelled correctly. It refers to the act of acquiring or obtaining something.