I'm just going to quickly explain this person's powers and abilities, and what CR do you think is about right for someone like this. If you want to suggest what class he is or give advice on how to build this, that's cool, too.
He is a warrior who wears a magical breast plate, and wields a magical short spear and shield. He's also extremely strong, being able lift as much as 25 tons over his head while still being able to run. He is able to smash down manufactured walls made out of marble, stone, concrete etc. without much effort with his hands in one blow. The warrior is capable of jumping up to 50ft. in the air, is capable of taking a direct hit from a rocket launcher for minimal damage, and can create shockwaves that destroys the ground up to 100ft. in diameter from a single powerful strike with his weapon against his foe. Firearms from trained soldiers would have little to no effect against him if he is to shot by one of them, and even has the reflexes necessary to parry firearm attacks with his shield from multiple people at once.
There's my quickly thought up warrior's abilities in a nutshell. What would you put him at?
I'll try to create this guy soon by strictly using the books and posting it here.
Just with the strength, your warrior will need to have more than Str 30 and above AND a permanent ant haul spell to lift these 25 tons. With this strength and a few monk level, he can hit as with adamatium weapon, bypass hardness and destroy pretty much what he want. For the shockwave...I don't know. Monks have very high touch AC, so maybe it would explain this warrior efficiency against firearms.
I don't have any idea for a CR, it will depend of the number of class level and the bonus you will have to throw on it.
Well I do have the stat block for this guy, now. What I really wanted to do is see what other peoples interpretations of this description would be. Another part of it was to get people to guess the CR of this guy, based off of this description of him. Just guessing the CR alone would have been great for me because I'm interested in people's guesses and why.
I didn't really write it out the way I intended, lol.
I'm going to approach this from a mechanical approach: what is the lowest-CR NPC that I could build who can actually meet this description? I will presume that he's supposed to be human and doesn't have outlandish templates. However, I will use the advanced template.
He is a warrior who wears a magical breast plate, and wields a magical short spear and shield.
The suggested magical weaponry, even if we presume only +1 enhancements, comes out to about 5000 GP in equipment. If we presume a few other miscellaneous items that individually cost on the order of a few hundred GP each, then that corresponds to the wealth level of a CR 6 character. So that's our lower bounds based on his equipment.
He's also extremely strong, being able lift as much as 25 tons over his head while still being able to run.
As Kelazan mentions, your strength is positively phenomenal. 25 tons is 50,000 pounds! For a medium sized creature without magical enhancement, this would require a strength score of 55. So magical enhancements are agiven. Even with a permanent ant haul, you'd still need a strength score of 47. Adding a permanent enlarge person lets us take the strength requirement down to 42, which is more RAW-legal territory.
Hitting this threshold will be difficult. If we presume PC stats for a baseline of 20 to strength, we still need +22 from other sources. First let's pick up the easy ones: a one-level Barbarian dip gets us +4 from rage, a one-level Alchemist dip gets us +4 from mutagen, and the advanced template (a +1 CR template) gets us +4 to all stats. We still need +10 on top of this, though, and that's where it starts to get expensive.
I'd welcome anyone who can do this with less of a CR investment, but it seems the lowest CR way to get 42 strength on a human is to start with PC stats (+1 CR, baseline 20 strength), PC wealth (+1 CR, +6 strength from belt), the advanced template (+1 CR, +4 strength), a Barbarian 11 / Alchemist 1 for greater rage and mutagen (+10 strength, +3 strength from level-up, baseline CR 11). That gives us CR 14 minimum for this level of strength.
He is able to smash down manufactured walls made out of marble, stone, concrete etc. without much effort with his hands in one blow
Masonry has a break DC of 35. With the aforementioned 42 strength he has a +21 strength modifier, with a +4 bonus for being large. He can take 10 and break manufactured walls.
The warrior is capable of jumping up to 50ft. in the air
High jumping 50 ft would require a DC 200 acrobatics check and a minimum of 50 ft move speed. The move speed we can do easily, but the DC is so far into the realm of impossibility within the rules that I just can't tackle it from that direction. I've tried, but the best I can hit is a +100 skill check, still a far cry from the +200 necessary to hit a 50 ft high jump. The only ability I can find to lower the DC is the ninja, but that requires 10 class levels so it's just not feasible.
Power-wise, though, this isn't actually as impressive as it sounds. Many classes have ways to access to flight as early as the 5th level. So if you were to sneak in a homebrew rage power that makes this possible, I wouldn't even touch the CR. It's just not a powerful enough ability.
is capable of taking a direct hit from a rocket launcher for minimal damage ... Firearms from trained soldiers would have little to no effect against him if he is to shot by one of them
Given we're already above 10 hit dice, any reasonably high constitution score can tank some amazing damage. With the invulnerable rager archetype and 10 levels of barbarian, we already have DR 5/- so most mundane attacks by non-magical foes will barely scratch him. No further CR adjustment necessary.
and even has the reflexes necessary to parry firearm attacks with his shield from multiple people at once.
Is there a feat that lets you add your shield bonus to touch AC? I was sure it existed, but can't find it. Anyways, just a feat investment as far as I'm concerned and not a CR adjustment.
and can create shockwaves that destroys the ground up to 100ft. in diameter from a single powerful strike with his weapon against his foe
Sounds roughly like the Earthquake spell. I'm not aware of any way to get it as a SLA or equivalent ability (although frankly it sounds like it could make a really cool rage power for a high-level barbarian). Once again, power-wise I'm not sure this merits a CR adjustment. So long as he paid a high-level rage power for it, I think this is okay.
So final verdict: CR 14 minimum