You cannot directly see a list of people who blocked you on WhatsApp
Check whether their last seen or online status is no longer visible
Check whether their profile photo has disappeared or stopped updating
Check whether their About info is no longer visible
Try sending a message and see whether it stays with one check mark only
Try making a WhatsApp call and see whether it does not connect
Try adding the person to a group and see whether WhatsApp prevents it
Compare behavior from another account if you need confirmation
Respect privacy and avoid repeated contact if you suspect you were blocked