hardest
"Hardest" is the superlative form of the adjective "hard" — it means the most hard. It has two main senses that mirror the two core meanings of "hard": one about physical texture and one about difficulty or effort. You'll also see it used as an adverb, meaning with the most force or effort.
Sometimes 'hardest' describes situations that are the most emotionally heavy or painful — not physically difficult, but mentally or emotionally draining. This is a figurative extension of the 'difficult' sense.
everyday language, emotional contexts · Modern, widely used · figurative