んじゃなかったか => shouldn't have... N4
Regret
いらっしゃる => to be; to come; to go (polite version) N4
ゃしない => Don't/Doesn't A (at all) N1
Will, Decision, Doing
ちゃった => to do something by accident, to finish completely N3
じゃないか => right? isn't it? let's~; confirmation N4
Speculation
じゃないか / ではないか => right? isn't it? N3
Confirm
じゃないか / ではないか => right?; isn't it? (Criticism) N3
Criticize
んじゃないか => right? isn't it? let's~; confirmation N4
Confirm
じゃありませんでした => was not, were not N5
Emphasize negative meaning
じゃないか / ではないか => right? isn't it? let's~; confirmation N3
Surprised
しかし => But, nevertheless N5
Change the subject of the story
んじゃ => If ... then... N4
Condition (hypothetical condition)