Tardigrades were placed in the "extremophile" class with good reason. If anything could survive a truly catastrophic impact event, I'd say the smart money goes on the lowly "water bear" to win. :)

Tardigrades are not "extremophiles", which refers to organisms that live (grow, reproduce) in "extreme" environments ("phile" = "like, love"). Tardigrades can temporarily survive some rather extreme conditions, but they generally require fairly ordinary environments to actually live. (As suggested by common names like "water bear" and "moss piglet".)