Hashashin are the origin of the word "assassins". It was Shia Islam sect known as Nizar Ismaili and were known for assassinations. Active during crusades (targeting both crusaders and other muslim) and were destroyed by Mongols.
I wouldn't know what to say. Guess depends what "warrior life" means. Like if it is healthy life style, physical fitness and ability to fight (preferably in self defense of course) then it would be an ok lifestyle.
And I wouldn't really call bodybuilders warriors, MMA ok those would be more fitting. I do have more respect for actual soldiers though, those that fight to protect.
Actually Greeks and Romans too were familiar with martial arts, at least some forms of wrestling and boxing. Unsure about dietary habits though I suspect nothing too complex.
And well regarding samurai diet like I said, they were nobles and they could afford all that food. Still surprisingly they were lot like western knights with bushido/chivalry code, both knights and samurai fighting on horses (though samurai used bows, knights saw ranged weapons dishonorable) oh and of course both are noble caste. Not to say that aren't differences but samurai are lot more romanticized because they are exotic. Oh and don't really know if meditation was factor since that is more mainland asia thing. Asian cultures aren't one singular thing.
Well vikings were definitely more organized then we give them credit. Though always thought it was first and foremost their naval capabilities that gave them the edge. As for drinking well seriously it is easier to list cultures that aren't alcoholic.
Well Spartans had very demanding training that started from age of 7 and lasted I think till 20 or something. And the only occupation was a soldier until they retired. Rest of the Greeks were not that brutal but as I said physical fitness was one of the top ideals.
Romans had mandatory military conscription until they switched to professional armies. Roman training is well documented and definitely was demanding. Though the quality did fall as time went which is true for greeks too.
No honest idea about vikings. Samurai were basically medieval knights and well nobles so I expect they had some combat training and had money to buy better equipment than common soldiers.
Well besides them actually being shorter than modern human they definitely were in top condition. Though I doubt they were as ripped as modern bodybuilders. For Greeks and Romans you can just look at their sculptures for the idealistic version of human body.