Zhèyàng de shèngkuàng, jiùsuàn bú shì juéhòu, yě shì kōngqián de.
A spectacle like this was unprecedented, even if it may not be the last of its kind.
Tips
usage
In the second sense 绝后 is the second half of 空前绝后 "unprecedented and never to be repeated": 空前 means nothing like it came before, 绝后 that nothing like it will come after.
culture
Having no son to carry on the family name was long seen as a grave misfortune, so in the first sense 绝后 is a heavy word, and wishing it on someone is a curse.
