Saving Throws: Saves are described beneath two categories: Strong and Weak. Strong saves are saves that will be used more often, due to how often effects in the game would trigger those saves. Strong saves are: Dex, Con, and Wis. Weak saves are: Str, Int, Cha.
You have two strong saves. I recommend changing one of them to a weak save.
Weapon Focus: Something 5e avoids is small, scaling, stacking modifiers to attack and damage. 4e was kinda built on the premise of small, scaling, stacking modifiers to attack and damage, and so it became a veritable arms race. A very complicated, tedious one.
5e avoids that now through the Advantage/Disadvantage system. Rather than granting +1s here and there under certain conditions, the DM is instead encouraged to say, "Dropping down from above? Advantage! Fighting waist deep in water? Disadvantage!"
A PC's accuracy caps at +11 at 17th level, +13 if you're an archer using Archery fighting style.
You're granting 1 1/2 proficiency bonus, i.e. 150%. At 1st level, that's an additional +3 accuracy.
So a player with a +3 ability score mod will, at 1st level, have proficiency bonus + ability score mod + weapon focus = 2 + 3 + 3 = +8. With Archery Fighting style, that's +10.
You're letting a 1st level Weapon Master archer have the same accuracy as a 9th level Fighter archer.
5e works on a system of Bounded AC/Accuracy, which is in contradiction with 4e, when AC and accuracy would reach obscene levels.
In 5e, player accuracy rarely exceeds +11, and AC is on average around 17 for all 20 levels of play. In 4e, accuracy could easily eventually exceed +30 and AC would eventually exceed 40.
Note how almost no class actually ever gets bonuses to accuracy outside of Fighting styles or the Barbarian's/Ranger's 20th level features.
Weapon Specialization: In 5e, weapon damage is typically increased in 3 ways: Increase the number of attacks, Add additional dice to the damage roll, and increase crit range. Stacking additional static mods to weapon damage is rather rare - the only example of this is the Warlock Pact of the Blade Lifedrinker Invocation granting Cha mod to pact of the blade weapon damage at 12th level.
Weapon Master Archetypes: Interesting, switching 10th for 11th of the Fighter's archetype progression.
Ability Score Improvement: The Fighter's progression. Just noting it for posterity.
Extra Attack: How do you justify granting Extra attack at 10th level when the Fighter has to wait until 11th level?
Signature Weapon: Repeat argument regarding small, static, scaling mods to attack and damage.
Improved Critical/Superior Critical. How... boring.
I am concerned about how every single class feature so far has just been boosts to attack and damage. At least the Fighter still had Second Wind and Indomitable.
Swordsman: Pommel Strike. This is a million times better than the Monk's 5th level Stunning Strike. Stunning strike consumes the monk's limited Ki resources, the DC is going to be a lot lower than DC 8 + damage dealt, and the stun only lasts until until the end of the monk's next turn.
Duelist's Parry: Mm... functional.
Intelligent Warrior: So you gain proficiency in intelligence saves for the duration of making an attack as a reaction against someone missing their attack against you?
I recommend making it either you can make a reaction attack or you gain proficiency in intelligence saves. After all, Rogues have to wait until1 5th level to gain an additional save, though it is the very valuable Wis save.
Vicious Riposte: What the heck is "Bleed" damage?
Sword Master: So a slightly better yet slightly worse version of the 1st level spell Compelled Duel, that ends as soon as either one of you hits each other with a single attack? Hardly what I consider capstone material. At best this is a 3rd level feature.
I am extremely concerned about how every single Swordsman subclass feature is a combat feature.
5e DnD is composed of three pillars: Combat, Exploration, Interaction. While combat is a very important part of the DnD experience (and the easiest to design features for), Exploration and Interaction are no less important. All classes have Exploration and Interaction features.
From Natural Explorer to Thieve's Cant to Know Your Enemy, classes are granted features to encourage actions and solutions that don't necessarily involve stabbing people.
So far your class doesn't have a single Exploration nor Interaction feature.
Destroyer: Tank. Do not grant feats as class/subclass features. Feats are inherently optional in 5e - you shouldn't force a DM to use one.
Strongman: Repeat argument about mod stacking.
Crushing Blow: Denied their Dexterity bonus on what? Attacks made with dex? AC? Dex saving throws?
Sundering Blow: No restriction on magical equipment? The opponent doesn't get to choose whether they take the damage vs risking their equipment? You constantly add multiple damage mods to attacks, and then expect opponents to somehow have a reasonable means to save against 8 + damage dealt?
Destroyer of Worlds: Not worth it at all. I'd rather just use Crushing Blow and Sundering Blow separately on the same turn - which I apparently can do, since Crushing Blow is a bonus action and Sundering Blow works on any attack I make.
Repeat argument about lack of Exploration/Interaction features.
Aim: An extremely nerfed version of the 1st level spell Hunter's Mark?
Archer's Wisdom: The Rogue's 15th level feature?
Pinpoint Accuracy: Why do you need this on top of granting a second Extra Attack at 10th level?
5e DnD has several tiers of play where a class' average damage typically grows dramatically. Those tiers are 5th, 11th, and 17th.
Martials get Extra attack, Multi Attack, Improved Divine Smite, etc. Casters get scaling Cantrip dice and higher level spell slots.
Monk nor Rogue don't get any unique damage growers at those tiers because their damage growth is built into their entire class growth, e.g. Martial Arts damage die and Sneak Attack.
This Weapon Master relies on Extra Attack to increase its average damage to appropriate levels. It doesn't need things like Pinpoint Accuracy.
Multishot: I'd really rather just fire arrows normally rather than use this clunky mess.
Bring the Rain: No such thing as "Standard Action". Only Action.
So not only do you force an archer to move within tight melee range, you arbitrarily increase the feature's damage output on an effectively meaningless conditional at 18th level?
Repeat argument about lack of Exploration/Interaction features.
Conclusions/Concerns: Classes are more than an answer to the question, "How do I deal damage?" Classes are ways of life. They emerge out of the conditions of the world and universe at large. Rangers exist because there are wild frontiers to explore and defend against. Clerics exist because there are deities who desire to expand their influence. Paladins exist because there are deities whose wills needs to be enforced. Warlocks exist because there are powerful creatures who desire proxies of/puppets to their will. Wizards exist because there is magic to be learned.
Fighters exist because a peak, physically performing body is still an undeniable force on any arena of war.
Why do Weapon Masters exist? Why would a player ever choose a Fighter over your Weapon Master? How does a Weapon Master's class features help it interact with the world around it?
Additional note: Subclasses tend to not force you to use specific weapons, unless they're broad categories, e.g. Finesse and ranged weapons/melee weapons. A Champion Fighter can be just as good an archer as an Eldritch Knight Fighter, and yet still they both could just as easily go Sword and Board, or Two Weapon Fighting, or Dueling.
Try not to lock your subclasses into using specific weapons.
Compare and contrast what other classes get at what levels.
Seek to balance combat features with exploration and interaction features.