Court configuration aside for all four sports... For strokes and general play, squash and Racquetball are most similar. For court strategy and the value of physical conditioning, Badminton and squash are most similar.
racquetball and squash
for APEX... volleyball
Racquetball originated from the sports squash, handball, and paddleball.
Racquetball originated from the sports squash, paddleball, and handball.
maybe....
Racquetball
Racquet sports (squash, badminton), handball and volleyball all have major similarities to tennis.
The sports were squash and handball.
Badminton Racquetball/Squash, Handball/Wall-ball Tether-ball Croquet, Horseshoes Pool Ping-Pong Bowling Fencing Billiards Boxing Tennis Darts
Tennis, Squash or racquet ball.
Prince sports
I know you can win a rubber in squash and Racquetball but not sure about what other sports