Learn Turkish: O bir öncü, hatta bir kahraman olarak görülüyor. - He is seen as a pioneer, in fact, as a hero.

Hatta is an escalating conjunction, meaning 'even', 'in fact', or 'moreover'. It builds on what was just said to make a stronger statement. Here, it escalates the idea from him being a 'pioneer' (öncü) to the much stronger claim of him being a 'hero' (kahraman).

Could I put olarak after öncü as well?

You could say O bir öncü olarak, hatta bir kahraman olarak görülüyor, but dropping the first olarak sounds much more natural. In Turkish, when listing things that share the same grammatical function or postposition, you usually only need to add that helper word to the final item in the list.

How is the verb görülüyor formed?

It is the passive form of görmek (to see). The -ül- suffix makes it passive, so görülmek means 'to be seen'. Adding the present continuous ending -üyor gives us görülüyor (is seen / is being seen).

Why do we need bir before both nouns? Don't we drop it for professions?

While Turkish usually drops bir when stating someone's literal profession (like O doktor for 'He is a doctor'), here 'pioneer' and 'hero' are being used as descriptive analogies, not standard job titles. Repeating bir after hatta also adds rhetorical emphasis to the escalation.