I can give you several sentences.
Suddenly, the tribal drumming stopped.
No, "suddenly" is not a complete sentence. It is an adverb that describes how an action is performed in a sentence.
Suddenly, a sharp rap was delivered to the door.
I was in the living room on day, and suddenly the lamp flicked on on its own.
The battling boas were twisting and writhing in the mud, when suddenly an alligator appeared!
Suddenly, I found myself staring into the very maw of the huge shark.
Ablactation occurred suddenly when her son refused to breastfeed at 15 months.
She stopped at the red light before continuing on her way.
I was suddenly taken aback by quite an unusual sight. That's an unusual design.
i was suddenly surrounded by a group of ninjas! or if you want a actually possible/boring answer i was surrounded by trees
Yes, if it is the first word of the sentence.
Suddenly she lashed out menacingly