prime; conspicuous
これは市場失敗の最たる例だ。
This is a prime example of market failure.
汚職は党衰退の最たる原因となった。
Corruption became the most conspicuous reason for the party's decline.
ストレスが彼の体調不良の最たる要因だった。
Stress was the foremost factor in his poor health.