vaikeinta
Vaikeinta is a Finnish word that functions as the partitive singular form of the superlative degree of the adjective vaikea, meaning “the most difficult.” It is used to describe the most challenging thing or aspect in a sentence, often when the noun it modifies is in the partitive case or when the predicate requires a partitive complement.
In practice, vaikeinta appears in sentences that compare difficulties or identify the utmost level of challenge.
Vaikeinta is distinct from the non-superlative forms of degree in Finnish. The positive form niin perusteella
See also: Finnish grammar, degree of comparison, partitive case, predicative adjectives.