Happen (verb) vs Coincidentally (adverb) 
Hit (verb) vs Suddenly/ Out of the blue (adverb) 
Wrong (adjective) vs Unexpectedly/ Accidentally (adverb)

Examples
Happen vs Coincidentally
Verb: Games happen during the summer.
Adverb: Coincidentally I won the game. 

Verb: Rain happened yesterday.
Adverb: Coincidentally it is raining now.

Hit vs Suddenly
Verb: The phone fell and hit the floor. 
Adverb: Suddenly I lost the phone. 
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Verb: I saw the lightweight strike. 
Adverb: Suddenly I saw lightning.

Wrong vs Unexpectedly
Adjective: They brought the wrong laptop. 
Adverb: Unexpectedly the laptop broke down. 

Adjective: I deleted the wrong number. 
Adverb: Accidentally I deleted the number.