If the attack of the opponent is 100, and my Pokemon has intimidate, how much does it reduce the opponent's attack to? (and also, does it reduce special attack too?)
Intimidate lowers Attack by one stage. This multiplies the original Attack stat by 2/3 (or 66/100 in Generations I and II), meaning a Pokemon with 100 Attack would have 66 following an Intimidate drop.
Stat modifier (Bulbapedia)
It would lower it to 75. It lowers by 1/4.