Adaptational Heroism: Though still retaining some of their flaws (arrogance, contempt for humanity, etc) the Eldar also haven't committed the same atrocities as their mainstream counterparts and do have moments of genuine nobility.
Only Sane Man: From his perspective anyway, outright saying that he's "the only person here who's got any sense".
Psychic Powers: His specialty, and one he has mastered. It's not completely fool-proof though, as he cannot read the minds of people who he does not know exist. He can also read the minds of everyone in the universe for only a short period of time before the overload fries his brain. Finally he cannot read the minds of those corrupted by Chaos' influence for an extended period of time.
Red Is Heroic: A mild case. Asurmen, one of the less arrogant and xenophobic Phoenix Lords, wears a red cape.
Red Right Hand: Invoked but also subverted. Karandras has a crab-claw in place of one of his hands, but rather than show him to be a servant of Slaanesh, it shows how the Prince of Pleasure tried and failed to convert him. Karandras wears it proudly as proof of his victory over Chaos' influence.
Scary Scorpions: Karandras has this aesthetic, as befitting of his status as the leader of the Striking Scorpions
Good Is Not Nice / Jerk with a Heart of Gold: Like all other Eldar he comes off as mean, racist, and cold-blooded to the humans, but also risks life and limb to get the surviving members of Hastati Squad off-planet.
Helmets Are Hardly Heroic: Inverted. Their soldiers all wear helmets, most of them of the "full-face covering" variety, and yet they are one of the two good races in the story, the other being the Eldar.
Heroic Sacrifice: Two: first Vickers attacks a group of Grunts and Chaos Space Marines to try and buy his squadmates time to flee, and then later when Thomas Lasky distracts the Hunters that Endewan was fighting, giving him time to finish them off. In both cases the performer of the sacrifice ends up dead.
We Need a Distraction: Thomas Lasky distracts a pair of Hunters that were fighting Endewan but unfortunately dies in the process
The Admiralty Board
Authority Equals Asskicking: Like the Eldar's Phoenix Lords, they fit this to a T by virtue of being both the leaders of the Space Marine Chapters and also by far the most powerful of the human's fighters.
Jerk with a Heart of Jerk: Leads the reinforcements that come to Thel and R'tas' rescue, but it turns out that it wasn't his idea and that if it were really up to him he would have just left them to die.
Authority Equals Asskicking: He and his fellow Zealot R'tas are the only ones to survive an attack by Necrons. Granted, they would have died had reinforcements not shown up, but it's still telling that they lasted longer than all of their subordinates
Authority Equals Asskicking: He and his fellow Zealot Thel are the only ones to survive an attack by Necrons. Granted, they would have died had reinforcements not shown up, but it's still telling that they lasted longer than all of their subordinates
Noble Demon: As close to one as the Covenant aliens get.
Old Friend: Him and Thel here, to the point that R'tas outright says that he's proud to meet his end at his side when it looks like they're going to die
Pet the Dog: Expresses genuine gratitude towards Sindri upon learning that he was the one who got R'tas and Thel reinforcements and saved their lives from Necrons
Adaptational Badass: Inverted. Here they lack their incredible Healing Factor and are not quite as invincible as they are in actual 40k continuity besides. But at the same time they're still incredibly dangerous and more than a match for the Eldar, humans, Covenant, and Daemons
Curb-Stomp Battle: Dished one out to a small army of Covenant and Daemons, killing all of them except Thel and R'tas and having over two dozen soldiers to spare. The surprise arrival of Covenant vehicles managed to destroy them though.
Composite Character: The Necrons having the role most commonly held by the Sentinels and in Halo 4 the Prometheans
He Who Fights Monsters / Knight Templar: Programmed to contain the Flood and other servants of Chaos...at all costs. This includes killing any and all beings who can "facilitate a wide-spread infestation". This includes humans and Eldar
Made of Iron: A somewhat literal example. They're so durable that one wasn't completely destroyed by a plasma grenade stuck to it's head. It did still take it down though. Others managed to be destroyed by the Eldritch flames of the Hunter's arm cannons. Even the Necrons have limits.
No Body Left Behind: What tends to happen to people who get hit with their disintegration weapons
Retcon: Here the Necrons were apparently creations of the Forerunners
Good Colors, Evil Colors: Notably when pleasant his "eye" is gold in color but when calling the Necrons into battle and commanding them it becomes the same green as the Necrons weapons and power. When actively fighting or enraged, the "eye" becomes red
Killer Robot: Shown to be perfectly capable of fighting and outright kills an Eldar Farseer with one shot