-ster as a common noun suffix:
* Master: One who has attained skill or knowledge.
* Bester: The best one.
* Youngster: A young person.
* Songster: A person who sings.
* Spinster: An unmarried woman (now considered outdated).
-ster as a derogatory suffix:
* Gangster: A member of a criminal gang.
* Blusterer: A person who makes loud, empty threats.
* Trickster: A person who deceives others.
* Monster: A creature that is frightening or grotesque.
* Quackster: A person who pretends to have medical skills.
* Slobberknocker: A person who is foolish or clumsy (slang).
Other words ending in -ster:
* Minster: A cathedral or the head of a cathedral.
* Cister: A water reservoir.
* Cluster: A group of things.
* Fester: To rot or decay.
* Roster: A list of names.
Important note: The "-ster" suffix can often be considered informal or even derogatory, so it's best to use it with caution and awareness of its potential connotations.