Things Adam could/should he have done differently, might include.
Pick up a rock and dash in the head of Serpent before it could further entice Eve.
Runaway and find God/call pout to God in a loud voice and tell Him what was happening/make Him aware of it.
Remind Eve that while she could touch the fruit and examine it, she wasn't to eat it, and that the Serpent, while a know-all, didn't know everything.
Smack the fruit out of her hand, when she went to bite it.
Let Eve do as she pleased, and wash his hands of her.
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When Eve saw that the tree was good for food, and that it was pleasant to the eyes, and a tree to be desired to make one wise, she took of the fruit thereof, and did eat, and gave also unto Adam who was with her; and he did eat as well.(Author unknown)
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Image depicting Adam's point of view.