This is the 4578th most frequent German word.
schwersten
"Schwersten" means "heaviest" or "most difficult," depending on context.
The word 'schwersten' in this sentence acts as the superlative form of the adjective 'schwer', describing the tasks as the most challenging among others.
Ich habe die schwersten Aufgaben erledigt.
I have completed the most difficult tasks.
Here, 'schwersten' is part of the phrase 'am schwersten', indicating the superlative degree applied to the verb, expressing maximum difficulty encountered.
Unter den Bedingungen war es am schwersten zu arbeiten.
Under those conditions, it was hardest to work.
The word 'schwersten' in this sentence refers to the weight of the book in the superlative form, indicating it is the heaviest amongst all.