A couple of notes: This subclass has 2 features that involve being attacked, so I will assume this class is intended to be for a melee ranger as opposed to a ranged ranger, in order to take advantage of these abilities. It is perfectly fine for a subclass to specialize with one weapon type over another, and I will be reviewing based on that.
Balanced, though not always effective.
I'll break down each feature, then summarize.
A Similar 3rd level ranger subclass features can be found with the Gloom Stalker feature Dread Ambusher (Xanathar's p.42-43):
...If you take the Attack action on that turn, you can make one additional weapon attack as part of that action. If that attack hits, the target takes an extra 1d8 damage of the weapon's damage type.
This would likely would match First Strike's damage from 5th to 10th level, but First Strike would exceed beyond 11th level due to the extra damage; I think that is okay, as Dread ambusher has a few other bonuses. I think this ability is balanced.
This Feature is nice, though it may fall into the Tank Fallacy: the better your defenses, the less likely you are to be targeted. With it already being limited to your favored enemies, it may not see a lot of use besides an initial swing, before the foe changes targets. (Yes, it is not typical of the Ranger to be a parties tank, however they do have a d10 dice roll, and are likely able to take more hits than any full casters in the party)
Master of thy Enemy (MotE):
I think this is a great feature. An additional favored enemy is always needed for the Ranger. At 11th level, an optimized character should have +9 chance to hit on a standard attack. Increasing this to +11 means you are now 22% more effective, and you get some extra damage.
Most other ranger abilities at this level are some form of an additional attack: the Hunter makes as many attacks as there are present enemies in range, the Gloom Stalker and Horizon Walker get an extra attack (conditionally), the Fey Wanderer gets an ally capable of making an attack, and the Beast Master gets an additional attack for their companion.
If you are a dueling Ranger, your optimized average damage at 11th level should be 1d8+7, an average of 11.5 damage per hit. All of the above features give you (roughly) an additional attack, which, for simplicity, we will assume is the same damage average. For MotE, you are given +2 damage, but you are also 22% more effective, so assuming that I know how to do useful math:
11.5 * 3 attacks = 34.5 "standard"
11.5+2 * 2 attacks * 1.222 effectiveness = 33 damage
For Two Weapon Fighting, we have one more attack to consider, dealing 1d6+5 damage, an average of 8.5:
8.5 * 4 attacks = 34 damage "standard"
8.5+2 * 3 attacks * 1.222 effectiveness = 38.5 damage MotE
And for Archery, +2 on attack rolls increases the Rangers effectiveness: your additional effectiveness from MotE is 18.2%, a total of 40.4%:
9.5 * 3 attacks * 1.222 effectiveness = 34.8 damage "standard"
9.5+2 * 2 attacks * 1.404 effectiveness = 32.3 damage MotE
So its damage slightly less for Dueling and Archery, and somewhat more for Two Weapon Fighting. I think this is as close to balanced as you are going to get, without a major change to the feature.
I am assuming here the reaction attack is a weapon attack, and requires the target to be in range of said weapon.
This is a good feature, but like the 7th level feature I worry this will fall under the tank fallacy: why is an enemy going to target this Ranger when they are heavily punished for it, when there are other combatants in the party they can target instead? As with Defensive Tactics, while the feature is interesting and balanced, it is not likely to see a lot of use, provided the DM is playing the enemy combatants intelligently.
This subclass is balanced. However, its defensive features will likely not come into play frequently, due to your enemies avoiding fighting you in order to not be punished. What you may want to consider is changes to encourage taking advantage of these features.
Some subclasses that do a good job of working as a tank are the Barbarian's Path of the Ancestral Guardian, and the Fighter's Cavalier. These subclasses have ways to punish an enemy for not attacking them, encouraging themselves to be the center of attention on the battlefield. While a 'tank' may not have been your intention with this subclass, I feel it is the best way to adjust these features without overhauling the subclass.
My suggested changes will only be to Defensive Tactics, and Retaliation:
At 7th level, When your favoured enemy makes an attack against any creature within 5 feet of you, including yourself, you can use your reaction to impose disadvantage on the attack roll.
This makes the feature a bit more versatile, and will overcome the tank fallacy as the disadvantage will apply to all creatures nearby, not just the Ranger.
At 15th level, you have learned to punish those who harm you with uncanny speed. If you use your Defensive Tactics feature and the attack hits the target, as part of the reaction you may make a melee attack against the attacking creature. If this attack hits, it deals an additional 2d8 damage of the weapon's damage type.
This again works to overcome the tank fallacy while still applying the same defensive advantages to the ranger. I removed the advantage granted by this feature, as I think the ability to use this on your allies as well as yourself is enough from the feature.