Step 1: Read the description carefully.
The clue is: a person who believes that pleasure is the highest good. The main idea is putting pleasure above everything else.
Step 2: Recall the matching philosophy.
The belief that pleasure and happiness are the most important goals of life is called hedonism. A follower of it has a related name.
Step 3: Check option Stoic.
A stoic stays calm and bears hardship without complaint. This is about self-control, not seeking pleasure, so it is wrong.
Step 4: Check option Cynic.
A cynic distrusts the motives of other people. This has nothing to do with pleasure, so it is wrong.
Step 5: Check option Ascetic.
An ascetic gives up worldly pleasures and lives a simple, strict life. This is the opposite of seeking pleasure, so it is wrong.
Step 6: Pick the matching word.
A hedonist treats pleasure as the highest good, which matches the clue exactly. \[ \boxed{\text{Hedonist}} \]