From the Super Mario Wiki
The Unlucky Space is a space that first appears in Mario Party 9. Unlike Lucky Spaces which reward the Captain for landing on it, Unlucky Spaces serve as their negative counterpart, penalizing any Captain unfortunate enough to land on one. Typically located next to a red Warp Pipe, an Unlucky Space will make a Piranha Plant appear and will force the Captain to travel down the Red Pipe into a cavern with six Mini Ztar Spaces. The Captain must then roll a standard Dice Block and move accordingly; higher numbers leading to spaces with a greater loss of Mini Stars. After that, the Captain will return to the main board (not by Piranha Plant again, exiting normally exactly like the Blue Warp Pipes). As well as ending their turn.
Unlucky Spaces are rarer than Lucky Spaces, and appear only in three boards; Toad Road, Bob-omb Factory and Blooper Beach. There is only one Unlucky Space in Toad Road, whereas Bob-omb Factory and Blooper Beach have their Unlucky Spaces on branching paths that Captains either can or cannot avoid.
On Blooper Beach, there are also two consecutive Unlucky Spaces just before the last fork of the board that causes a different event from the above to occur. Landing on any one of them will cause the nearby Blooper statue to activate and create a whirlpool, sucking the vehicle to a path around it comprising of Mini Ztar Spaces and Dash Spaces. The players take turns getting out of the path to avoid losing excessive Mini Stars while the Blooper statue drags the vehicle two spaces back at the end of each player's turn.
Only one Unlucky Space appears in Mario Party: Island Tour, right in the path of a sleeping Chain Chomp.
Names in other languages
||不運なスペース Fuun'na supēsu
||Bad Luck Space
||Bad Luck Space