Shaolin Legandary Elders Great Power Comes with Great Responsibilty - Buddhism Zen According to the Chinese History, subject refers are the 5 survivor of Shaolin legendary grand masters.
https://en.wikipedia.org/wiki/Bak_Mei
In history, Ng Mui was escaping from temple to temple while Bak Mei joined the military and lead the troop to kill/eliminate other shaolin Temple.
What if those 5 elderly grant masters put down status as Monk/Nun, join the military with righteous intention and good deed/win win term and condition with Emperor. In this case, path to Nirvana likely unable to achieve.
https://en.wikipedia.org/wiki/Hall_of_Kshitigarbha
&quot;Until the hells are empty (of suffering beings), I will not become a Buddha.&quot;
(「地獄不空，誓不成佛。」)
The intention is to influence the Emperor/General to minimize the damages and at the same time not losing the Empire base on Buddhism teaching? By right those grand masters should equipped with Buddhism/Taoism super natural abilities then should not be difficult.?  If it doesn't work and disagreement from Emperor, then quit the military.
If influence to the emperor was success and damages was minimum say 50k killed instead of 500k. So it saved 90% lives and many of them inspired and follow grand master learning Buddhism. Then Buddhism get greater influence and follower multiples.
In this case, can the 50k person killed is waived from Bad Karma?
Those grand master should have high Buddhism wisdom power to influence and change ?
This might applicable to corporate working life now or politics world.
&quot;Proper means&quot; has nothing to do with the Buddha-Dhamma, good householder, as Shaolin hasn't. To call oneself Buddhas monk, yet not even serious in regard the precepts and dedicated to win and gain, actors for trade, is simply a thief. May no one get fooled by fools.
Wrong deeds stay wrong deeds, precepts are simple and no go, as well as kamma doesn't argue around.
But in regard whether a mass-murder could become a saint, Arahat, reaching Nibbana in present life: yes (as long as not killed mother, father or an Arahat). One may get familar with

Angulimala: A Murderer's Road to Sainthood, by Hellmuth Hecker (2007; 12pp./37KB)
A biography in the BPS's &quot;Lives of the Disciples&quot; series. A brief biography of Angulimala, the notorious bandit who was transformed by the Dhamma and eventually became an arahant.

Results of actions are still arising for Saints, but taken with ease, impersonal untouched by Arahts.
[Note that this isn't given for trade binding to the world, stacks, exchange... but for rekease from this wheel]