A dramatic turnaround; a major reversal — when the situation or outcome suddenly changes, often in a surprising comeback.
試合は終了間際のゴールで大逆転となった。
The match became a dramatic turnaround with a goal near the end.
選挙では最後の演説が効いて大逆転が起きた。
In the election, the final speech had an effect and a major reversal occurred.
映画のラストで主人公が巻き返す大逆転劇が描かれる。
At the end of the movie, there is a great comeback where the protagonist turns things around.