Unquestionably, Captain Ahab is in charge of the whaling ship, Pequod.  As Peleg describes him, “He’s a grand, ungodly, god-like man.” From Peleg's descriptions, Ishmael feels both pity and awe for Ahab, suggesting that Ahab may be a tragic hero. In Chapter 26, Melville employs the classic device of apostrophe in exalting the first mates and captain of the Pequod:

If, then, to meanest mariners, and renegades and castaways, I shall hereafter ascribe high qualities, though dark; weave round them tragic graces; if even the most mournful, perchance the most abased, among them all, shall at times lift himself to the exalted mounts; if I shall touch that workman's arm with some ethereal light; if I shall spread a rainbow over his disastrous set of sun; then against all mortal critics bear me out in it, thou Just Spirit of Equality, which hast spread one royal mantle of humanity over all my kind!

In Chapter 28 when Ahab stands on the quarterdeck, Melville writes of him,

There was an infinity of firmest fortitude, a determinate, unsurrenderable wilfulness, in the fixed and fearless, forward dedication of that glance.

In Chapter 36, Ahab ascends the cabin-gangway to the deck and orders Starbuck to "send everyone aft."  When the seamen arrive, Ahab inspires the men with the desire to seek the great white whale who is but a "pasteboard mask" for evil. His questions are responded to immediately and fiercely by the crew; his orders obeyed.  He is respected and feared, for in his Shakespearean intensity, even Ahab admits in Chapter 28, “I am madness maddened!”

This madness, this monomania, drives Ahab to the detriment of others.  His obsession with the conquering of Moby Dick causes Ahab to become "a ravenous monster" that prevents reason.  When, for instance, in Chapter 128, Captain Gardiner asks Ahab for assistance in finding his son whose whale boat was lost in the chase after Moby Dick, Ahab refuses him aid because he wants to pursue the white whale.  Later, as Ahab talks with Starbuck in the later chapters, he realizes the dangers of his pursuit; however, he feels compelled to continue.  he even questions himself,

What is it, what nameless, inscrutable, unearthly thing is it; what cozening, hidden lord and master, and cruel, remorseless emperor commands me; that against all natural lovings and longings, I so keep pushing, and crowding, and jamming myself on all the time; recklessly making me ready to do what in my own proper, natural heart, I durst not so much as dare? Is Ahab, Ahab?

Having used Pip in a whale boat, Ahab has endangered his life and caused the cabin boy to lose his mind. Finally, all but Ishmael lose their lives in the obsessed pursuit of revenge by Captain Ahab, who, though inspiring, is a tragic man and not a good leader.