What is the attitude displayed by Captain Nemo concerning his general outlook on the world and how do you know? Twenty Thousand Leagues Under the Sea
I would say that Captain Nemo's general outlook on the world and mankind is a mixture of general aversion and hatred. It can be tough to make out exactly what Nemo's outlook is, because he is presented as a fairly private character. He keeps things close to the chest, and the book does not give many details into his history before the Nautilus.
A reason for his general aversion to the world is that he built a special submarine in order to be more alone and apart from the world. To quote Nemo himself: "I am not what you call a civilized being! I have broken with society for reasons which I alone have the right to appreciate. So I do not obey its rules, and I ask you never to invoke them in my presence again! "
It's not that Nemo hates all people though. He loves his crewmen and is deeply concerned and sorrowed over any of their deaths.
His hatred of the world is evidenced by the fact that his submarine is more than a way to achieve solitude. It's a warship. He uses the Nautilus to sink ships and kill men. He obviously hates something of mankind to be so blood thirsty at times.