According to rules.
Players armed with a Ball&Chain can only take Move Actions.
At the start of a Block Action a player who ...
So you can't use multiple block on Fanatic.
But in the game you can in some cases.
A multi-block can be declared only at the very beginning, before any movement. You can make 2 specific blocks. This immediately ends the movement of the player, the player does not move anywhere in the end.
You can not choose if only 1 player in contact. You can not choose if one is standing, the second is lying down. You can not choose if it's your own + one opponent's player. You can not choose if you already moved.