What service brand has the most rigorous Boot camp training?

Only the Navy and Marines have Boot Camp. The others call it Basic Training. I don't remember being branded.

ohhhhhh, I am sure all the Marines here will say it's the Marines, of course. 

service branch?

Here in the Netherlands that would be the Commando's and Marines. They can be compared to US green berets

the Royal Marine Commandoes 32 weeks Basic training

The United States Marine Corps, for the U.S. Military.

The Hardest Boot Camp is the French Foreign Legion.

There are a lot of metrics you can evaluate to determine "most rigorous".  Let's look at duration:  Air Force & Navy, 7 weeks; Army is 10 weeks, US Marine Corps is 13 weeks.  Let's look at running:  Air Force & Navy, 1.5 mile run; Army, a 2-mile run.  US Marine Corps, 3-mile run.  Let's look after boot camp:  in the Army, Navy, Air Force you go to your primary school to learn your job.  In the Marine Corps you go to either Marine Corps Combat Training or the School of Infantry.  And always remember, no one "joins" the Marines, you become a Marine and that lasts a life time.

well the air force spends the most time in the field doing actual combat training

the marine corps spends the most time on drill, learning how to ,march and stand up straight

I would say the Marines. But your answer is ghosted.  Is this the shower you take your selfies in?