Which character openly objects to Captain Ahab’s obsession in Moby-Dick?

In the novel Moby-Dick by Herman Melville, the character who openly objects to Captain Ahab’s obsession is Starbuck, the ship's first mate.1

While other crew members are aware of Ahab's deteriorating mental state, Starbuck is the only individual throughout the narrative to voice his disapproval of the captain's increasingly dangerous and obsessive pursuit of the white whale. Despite Starbuck's persistent reluctance, Ahab remains committed to hunting Moby Dick regardless of the cost to the Pequod and its crew.1