The easiest Brutality I've found is Erron Black's default Brutality "Tunnel Vision".
All you need to do is finish the ending round with Erron's forward throw
,
or
,
+
and it will activate.
Fast way to boost this would to be if you have the "Brutality Kombat" Modifier, is to grab a second controller and go into Kustom Kombat and use said modifier, it makes it so that brutalities can be preformed at time, so all you need to do is a forward throw at the start of the match and you'll do it automatically.
If you only have one controller you can play regular tower with it set to 1 round, or try Test your Luck and keep spinning reels until you get Brutality Kombat and from there rematch with the same reels.