Just think what a world that would be. It isn’t normal and we should probably resist the temptation to inflict suffering on others whatever the circumstances.

I think there you need to be careful on definitions.

There are unbalanced relationships where one person has more power than another and treats the first person in a way that you or I might feel is improper. Then there is the clinical definition of sadism, this Sadism Disorder DSM-5 302.84 (F65.52). which is a whole different level of personality.

My guess is that for most people, clinical sadism is not the issue – it’s more the imbalance of power in a relationship.

And to directly answer your question, clinical sadism happens enough that it is defined in the DSM as a disorder, so – yes – it is normal enough to be described.

It’s a matter of degree. Feelings of wanting someone to suffer when you are in the middle of feeling an emotion of anger, particularly when you’re thinking they have just hurt you, is pretty normal. Enjoying fictional villains coming to a terrible end tends to be intended by the author, and is also “normal”.

Enjoying torturing the innocent, and delighting in causing and relishing the agony of others who don’t deserve it, is probably something you would want to examine what that’s about. Not that you should be thinking “that’s NOT NORMAL” and thinking that the abnormality is the thing to be worried about… that’s a societal mental illness in itself (fear of the abnormal)... But it is a sign of unprocessed trauma that would be good to process in a healthy way.

Sartre wrote about sadism and masochism in Being and Nothingness. He said sadism was an attempt to impose one’s will on someone else and masochism was an attempt to surrender one’s will to someone else. They are both attempts to be intimate with someone by forming a kind of meld. He said that both are doomed to failure. Do a search on Sartre in this article

Define “normal”.
Then you can decide if something is normal.

The word normal is relative, one would have difficulty explaining what normal is in a multicultural atmosphere.

Thanks for each interpretation. I think I can draw a line between sadism and vengeance.