adverb taking the 'to' particle, taru-adjective
boldly; resolutely; fearlessly
Describes taking action with firm determination and courage, often in the face of difficulty or opposition. Used adverbially with と, or attributively as a たる adjective in formal writing.
He resolutely confronted the difficulty.
He boldly stood up and exposed the wrongdoing.
Even when facing difficulties, he maintained a resolute attitude.
Everyone was moved by his resolutely bold attitude.
大胆 focuses on boldness or audacity in general behavior, while 敢然 specifically conveys resolute courage in the face of difficulty.
敢えて shares the kanji 敢 with 敢然 but means 'daringly/deliberately doing something despite risk,' not 'boldly/resolutely' as a manner adverb.
Formed from the kanji 敢 (daring, bold) and the suffix 然 (indicating a state or manner). The exact historical derivation is uncertain, but it follows a classical Chinese pattern for forming adverbs/adjectives.