I said
fast attacks as in speed-based moves. While the second attack fits the description. We usually don't call it a blitz when you knock someone down and follow it up with a second attack. It has to be something like what Kaido did to Luffy in Kuri. Or what Luffy does to Hodi when he enters the fight:
Basically, when the opponent is in a position to defend, yet you're so fast or quick that he fails to react.