That flail is certainly the worst of the lot. Terrible impractical weapon with scant evidence of it ever being used by anyone.

There’s a two-handed version of the flail that is basically an agricultural threshing tool with spikes stuck into the head, which is much more plausible as a peasant’s weapon (very similar development process as the nunchaku, also a highly overrated weapon). However most weapons that feature a flexible rope/chain part in their design all suffer from the same drawbacks: difficult to control, and limited striking power.