Learn Finnish: Itse turvamies oli pelottavampi kuin päämies. - The bodyguard himself was scarier than the head of state.

In this sentence, itse is an intensifying appositive pronoun meaning the bodyguard himself. When used immediately before a noun to emphasize it like this, itse does not inflect. It stays frozen in its basic form regardless of the noun's case in the rest of the sentence.

How is the adjective pelottavampi formed?

It comes from the adjective pelottava (scary), which is actually the present active participle (the -va participle) of the verb pelottaa (to frighten). To make the comparative form scarier, the final vowel drops and you add the comparative ending -mpi, resulting in pelottavampi.

Both nouns end in -mies. What exactly does päämies mean compared to turvamies?

Turvamies literally means safety man (security guard or bodyguard). Päämies literally means head man. Depending on the context, it translates to a head of state, a chief, or a legal or business principal.

Could I express the comparison without using the word kuin?

Yes! You can drop the word kuin (than) and put the second noun into the partitive case instead. The sentence would then become: Itse turvamies oli päämiestä pelottavampi.