Which is correct, tougher, or more tough?

The correct answer is tougher.

When a word is monosyllabic, meaning that it has only one syllable, then its comparative form will be created by adding the suffix -er. Since the adjective tough has only one syllable, its comparative will be tougher. In case of words that have more than one syllable, such as beautiful, you would add more to create their comparative form: more beautiful instead of beautifuler.

the answer to this question

in ray bradbury's short story "a sound of thunder", mr. eckels's fearfulness leads to drastic consequences for the rest of the world.

in the story, mr. eckels, who is a hunter, hires a time travel company to travel to the age of dinosaurs. although he is excited for the hunting expedition at the beginning, when they reach there and mr. eckels sees the tyrannosaurus, he feels frightened. as he is afraid of the tyrannosaurus, he steps off the path although he has been warned not to do it. by stepping off the path, the entire course of the future is affected: mr. eckart alters the future by stepping on a butterfly, which causes a new man to be elected president in the future. in that way, it is mr. eckart's fearfulness what triggers 'the butterfly effect' and what leads to drastic consequences for the rest of the world.