The point of X-Ray is to assure that you win without allowing your opponent to break.
Example:
1) You get blown up and you're almost dead. However, this makes your meter build drastically.
2) Opponent has less than 50% of his life and he makes a mistake. You punish with X-Ray combo and win the round anyways.
The less meter your opponent has, the longer you can extend the combo before the X-Ray without him being able to break. If he already has two bars, you're better off doing the X-Ray right after you get an attack to connect, or punish directly with the X-Ray (no combo).
You can make HUGE comebacks with X-Ray. A 40% combo might not kill your opponent and he can break it. X-Ray will kill him and he can't break.
I don't recommend saving meter for an X-Ray with Nightwolf, but if you do have one and it's time to use it...
X-RAY COMBOS!
For punisher use this one:
Hatchet,
Hatchet,
,
= 52% (55% with JIP)
In most circumstances you should use:
Hatchet,
Hatchet,
,
= 50% (53% with JIP)
Hatchet,
Hatchet,
,
= 50% (53% with JIP)