The remaining Trophies/Achievements are typically earned through performing specific combat feats, or by manipulating the Nemesis System. None of the Warchief-related Trophies/Achievements can be earned until after you complete the mission "The Warchief" . Further manipulation of Sauron’s Army is only possible after the mission "Queen of the Shore" .
Climb to a really high place, and perform a "Strike From Above". A good spot near the beginning of the game is the northern spot of The Black Gate-just climb the scaffolding along the wall, lure an Uruk nearby by using Attract, and Strike From Above.
Set a Berserker on fire and kill them with an Execution. The "Double Charge" Ability will help immensely with this. Some might advocate using "Fire Arrow" to set the Uruk on fire, but it seems that if the Berserker takes enough damage to kill them from the fire, it won’t count, even if you kill them with an Execution before they "die".
Instead, find a Berserker near a camp fire. Shoot any accompanying Uruks to charge your Hit Streak ("Blade Master" makes this easier), then grab the Berserker, throw them through the camp fire, then perform an Execution on them. The Tower of Defense Epic Sword Rune will give you plenty of time to pull this off, if you’re having trouble.
Once you obtain the "Detonate" Ability, shoot camp fires and explosive barrels to catch Uruks on fire. This is such an effective means to get rid of Uruks that you’ll probably obtain this without even really trying.
When you get enough Power to unlock Tier 4 Abilities you can buy the "Death Threat" Ability. Grab a lesser Uruk and Dominate them, then press (Square) to send a Death Threat. Pick a Captain from Sauron’s Army to issue the Death Threat to and the Uruk will run off to deliver your message. The target will gain +5 Power Rating and a retinue of minions of the same type (Archers will get Archers, Defenders will get Defenders, etc.) Find the Captain you sent the Death Threat to and make good on it to earn this Trophy/Achievement.
Complete the mission "Queen of the Shore" to learn the "Brand" Ability. To earn this Trophy/Achievement you’ll have to Brand a Captain while in combat. Either incapacitate any nearby Uruks (using the "Wraith Flash" Ability is one way to do this). Another way is to find a Captain who has the "Vulnerable to Stealth" Weakness, and Stealth Brand them. There must be nearby hostile Uruks for this to count.
Complete the mission "Queen of the Shore" to earn the Brand Ability. Once you have this Ability you can Brand weakened Captains and Command them to join a Warchief’s Bodyguard. After that’s done, complete a Power Struggle to get them promoted to Bodyguard. Do this with five Captains, then complete the Warchief’s Showdown mission. When you confront the Warchief, your Branded Captains will attack him, and you’ll earn this Trophy/Achievement.
Warchiefs, like lesser Uruks, can occassionally have Fears. Exploit one in combat to earn this Trophy/Achievement. "Fear of Burning" is probably the easiest one to exploit.
You can earn this Trophy/Achievement in Udun, after the mission "The Warchief" . Your running objective will be to eliminate a number of Warchiefs, which is made easier by hunting down their Captain Bodyguards, first. After you kill all the Bodyguards (usually only one or two Captains) of two Warchiefs, you’ll get this Trophy/Achievement.
The key to this Trophy/Achievement is not dying, as time passes when you die, and in that time an Uruk can be promoted to Warchief. You can start killing Warchiefs after the mission "The Warchief" . If you kill all the Warchiefs save Ratbag, you’ll earn this Trophy/Achievement during the mission "The Black Captain" .
Pretty much what the description for the Trophy/Achievement says. Make sure there’s a vacant spot in Sauron’s Army, then get killed by some lesser Uruk. He’ll get promoted to Captain for his deed. Kill a Warchief, then let the newly-crowned Captain kill you again. Repeat until he becomes Warchief. Then complete his Showdown mission, confront him, and kill him. You can also Brand him after he becomes a Captain (complete the mission "Queen of the Shore" to learn this Ability), Command him to take a vacant Warchief spot, complete the Power Struggle necessary for him to get promoted, then summon your Warchief and kill him.
Brand a Warchief, then summon him. Command him to attack another Warchief and you’ll unlock a "Riot" Power Struggle, as well as this Trophy/Achievement.
To complete this successfully we need to liberate 30 Slaves in 180 seconds while riding a Caragor. The easiest way to do this is to fast travel to the Tirith Mesas Forge Tower during the day. From this tower head north and, with any luck, you’ll find a Caragor pouncing around in the flood plains here or in Celon Poros. Shadow Mount the best, and dominate it, then ride east through Celon Poros, freeing slave by killing their attendant Uruks. To do this quickly, use your bow, Drain your Caragor if you need more Elf-Shot, and stay out of melee combat. Head to the eastern edge of Celon Poros, then go north, either directly into the Cape of Nurn, or through the western edge of Watcher landing. Make your way up north through the Cape of Nurn, following the road, and free slaves up to the Nurnen Peninsula.
If you were lucky, enough slaves were around to unlock the Trophy/Achievement. If not, close the game, restart, and try again. It’s mostly a matter of luck if enough Slaves are in the area. If you aren’t successful, there’s a good chance the run will be sparsely populated with slaves immediately afterwards, hence quiting and retrying. This will obviously be easier with a fully upgraded Talion (especially if you have all the Focus and Elf-Shot upgrades). The Evenstar Epic Sword Rune (recover all focus when the Hit Streak is charged) and some River of Arrows Bow Runes (1% chance per level to recover one Elf-Shot after firing the bow) also come in handy.
Find Caragor cages and shoot the door to free them. Do this five times for this Trophy/Achievement.
Find hanging flanks of meat and shoot them to lure Caragors. Do this five times for this Trophy/Achievement.
Find Morgai Fly Nests hanging off of ropes and shoot them down to tormet Uruks below. Once a cumulative total of 20 Uruks have been affected, you’ll earn this Trophy/Achievement.
Spend Mirian and purchase two Sword Rune upgrades to score this Trophy/Achievement.
Spend Mirian and purchase three Dagger Rune upgrades to earn this Trophy/Achievement.
Spend Mirian and purchase one Bow Rune upgrade to collect this Trophy/Achievement.
This Trophy/Achievement unlocks when you obtain a level 25 Rune. Of course, we know that the Uruk’s Power Rating determines the base level of the Rune he drops, up to a maximum of 20, so how do we get those other five levels? Well, the level of the Rune is modified by various things. If the Uruk we kill is a Warchief, they’ll drop a rune two levels higher than normal. Obviously, to get a level 25 Rune we’ll need to target a Warchief. Other factors include sending a Death Threat (+1 Rune level), knowing the Uruk’s Strengths and Weaknesses (grab some Intel on the target for another +1 bonus to Rune level), if we exploit a Fear or Hatred during the fight (+1 Rune level), and if the Uruk killed us before (+1 Rune level).
There’s one rub, however-if you send a Death Threat to a Warchief, they will almost always drop an Epic Rune, which is a good thing, normally, but for this… not so much. Epic Runes don’t have levels, and won’t get us the Trophy/Achievement we’re looking for. If, however, you’re willing to grind out Runes, kill dozens of Captains, and score all the Epic Runes, they’ll start dropping normal runes. Time consuming, but it’s an option. Otherwise, find an Uruk with an easily-exploited Fear (Fear of Burning is the easiest one to exploit). Get killed by them, and they should gain in power. They will need to have a Power Rating of 20, which you can manage by getting killed by them repeatedly, or by helping them succeed at Power Struggles. Once they have a Power Rating of 20, get them promoted to Warchief, if they’re not already a Warchief (getting killed while a Warchief spot is vacant should do this).
You should now have gained Intel on the Uruk (needed to find out what their Strengths/Weakness are), gotten killed by them at least once, and raised them to the status of a Power Level 20 Warchief. Complete their Showdown Mission, and while in combat with them exploit their Fear of Burning by shooting them with a Fire Arrow (if they’re not immune to ranged attacks) or by luring them near an explosiving object and detonating it. Once done, kill them and, if you don’t get an Epic Rune, you should score a level 25 Rune.