Here is the full list of all 46 Knockdown the Ball achievements.
"1"
"12"
"11"
"10"
"RUINE"
"9"
"8"
"7"
"6"
"GROUND"
"LAVA"
"5"
"ICE"
"4"
"3"
"DEBRIS"
"1000"
"B"
"V"
"M"
"K"
"J"
"D"
"2"
"N"
"Q"
"Y"
"R"
"O"
"Z"
"F"
"G"
"TILE"
"W"
"I"
"E"
"A"
"L"
"U"
"P"
"H"
"C"
"S"
"T"
"X"
"0"