There was something interesting added to this game called "Critical Finishes"

They never had it in the previous Soul Calibur games, so it's definitely fun to experiment with, though difficult to use.

Critical Finishes are always a 1 Hit KO. It's extremely difficult to use against an enemy, since by the time you're able to use it, the opponent is dead anyway. Start by going into Training since both you and the enemy will have unlimited health, so you can keep trying until you get it.

Choose any character, I would suggest just starting with your best character, or someone that doesn't always get caught in their own combos. Maxi wouldn't be the best choice for this, since sometimes it's difficult to immediately stop a combo.
When you enter Training, press start and change the Free Style to option Vs. Cpu and best is to start with setting the enemy difficulty to easy. For a first time, don't start with Edge Master, I don't care how good you are, just start on Easy or Normal so you can experiment a little without having too many problems. Now go into the Soul Gauge option and turn the ENEMY Soul Gauge option to Empty. Yours can be full, blinking red, or just in the middle. Your Soul Gauge will NOT affect Critical Finishes in any way at all, the opponent though MUST have a blinking red Gauge, or Empty. When the Soul Gauge is flashing red, you have a chance to break your opponent armor. To do this, just continuously attack until red lightning surrounds the opponent and they will stagger back. When this happens, immediately press the Left Button (L1) and you will enter Critical Finish mode, then you can watch how the character you were using has their Critical Finish.

Again, this is very hard to use, so don't try it in every match. Only attempt it when your opponent has an empty Soul Gauge, otherwise you'll just get worse at the game.

Enjoy!