deep regret; bitter disappointment
A strong, formal expression of regret or disappointment, often used in written or formal speech. As a yojijukugo, it carries a literary weight.
His resignation is deeply regrettable.
It ended in a most disappointing result.
残念 is a common, everyday word for 'regrettable' or 'disappointing'. 残念至極 is a much stronger, formal, and emphatic version, often used in writing or formal statements.
A yojijukugo combining 残念 (regret) and 至極 (extremely). The exact historical derivation is uncertain, but it follows a common pattern of intensifying a noun with 至極.