Define "sheer power", please. His father, for one, is someone who surpasses him in terms of raw power.
As Anakin, yeah, when he couldn't even overpower Obi-Wan. As Vader, we know his limits.
And by sheer power, I mean his overall or acquired power. Simply put, what he's capable of using in a combat scenario. Call it what you want.
Moreover, Solo is only confirmed to be stronger than Vader by Invincible (compare Solo's duel with Aurra Sing to Vader's). Nothing suggests he is on par with the Emperor.
There are only two books between
Inferno, when Luke duels Solo, and
Invincible, when the whole thing finally ends. I highly doubt that Jacen grows in power all that much in such a short span of time, but fine, let's say he's weaker than Vader.
We know Vader's power to be, by word of George Lucas, 80% of what Sidious has as of the OT. Jacen, as of Invincible, is more powerful than Vader. Ergo, he has greater than 80% of the Emperor's raw power. Luke, with laughable ease, was capable of locking Jacen in stasis without exerting himself. Even assuming Jacen nearly doubled in applicable power, that's a mighty impressive feat considering the complete lack of effort, and means that perhaps with difficulty, he should be capable of doing the same to Vader and Palpatine, although the latter individual's vast Force-mastery should prevent such humiliation.
And I never said Jacen was on par with the Emperor in anything; I merely noted that he approached him in raw power, which it is apparent he does.
--
In the next instant, Caedus found himself flying across the cabin toward his observation bubble. Luke had not gestured, had not flinched, had not even shifted his gaze; he had simply grabbed Caedus in the Force and hurled him five meters into his chair.
"Don't lie." Luke started across the cabin. "I'm getting tired of it."
Caedus sprang out of the chair... or attempted to. Instead, he found himself struggling against an invisible weight. He felt as if he were accelerating to lightspeed with a faulty inertial compensator.
"Luke, you've gone mad." Caedus reached for the controls on the arm of his chair and discovered he couldn't even do that much. "You can't do this. I know you're having trouble dealing with Mara's death, but..."
"This has nothing to do with Mara, "Luke said. "And you're lucky it doesn't. If she were here-if she had known what you were using Ben for-there'd be pieces of you scattered along the entire length of the Hydian Way."
The irony of the statement was far from lost on Caedus, but he was too astonished-and too frightened-to take any pleasure in it. While it was true that Luke had taken him by surprise, it was equally true that he had done so with no visible effort-and that he was continuing to hold him with no apparent exertion.
Keenly aware that all that stood between him and a quick death was Luke Skywalker's much-strained sense of decency, Caedus let a little of his very real fear seep into the Force, just enough to seem properly alarmed.
--
Note: I was wrong about him talking to Ben. I didn't remember the sequence correctly, and believed it occurred just before the big duel.
--
"Luke, "Caedus called. "Aren't you forgetting something?"
Luke stopped at the door and looked back, the rage in his face now softening to what looked like remorse. "You're right. I should warn you that you'll have to crush the Confederation without StealthXs. The Jedi can support you no longer."
"What?" Caedus was so shocked that he tried to rise- and found himself as unable to move as before. "You can't desert now. We can end this war!"
"We could destroy the Confederation fleets and kill a lot of rebels, "Luke admitted. "But I don't think you can end this war, Jacen. I don't think you even know what it's about."
"That's absurd." Caedus did not understand how a man who had been fighting wars for forty years could be so foolish. "After their fleets are destroyed, Corellia and Both-awui will have to accept our terms, and once they've surrendered, the rest of the Confederation will have no choice but to come racing to rejoin the Alliance."
Luke shook his head and reached for the touch pad beside the door. "There's always a choice, Jacen."
"And if you go through with this one, you'll regret it." Caedus could not understand why Luke wanted to desert him just when they were on the brink of saving the Alliance, but he did know how to prevent it. "Have you forgotten the academy?"
The door opened. Instead of stepping through, Luke faced Caedus and spoke in a very calm voice. "I'm sure you're not threatening the younglings."
He pointed at the base of Jacen's meditation chair and made a tapping motion with his finger. The pedestal gave a loud whumpf, and the seat dropped a quarter meter.
"Because you really don't want to see me angry." Luke made the tapping motion again. The pedestal emitted a metallic shriek, and the seat dropped another quarter meter. "And I think you're smart enough to know that."
Luke tapped a last time, and the pedestal collapsed with a low loud crump, depositing Caedus on the floor with his feet sticking out in front of him like a child.
"But if you want to try me, go ahead and make that threat."
Luke lowered his hand, and the weight vanished from Caedus's chest. He could have leapt up to attack-had he been that foolish-but Sith were not slaves to their emotions. Avenging his humiliation could wait until after he had saved the Alliance.
Again, I wouldn't say that. Skywalker was critically injured by Solo during their duel.
Here's a list of
every wound suffered by Skywalker in the duel:
1) Roundhouse-kick to the chest, which hits his damaged lungs (from Lumiya) hard.
2) Jacen lashes him into the tendrils the first time. He cuts out almost immediately.
3) Jacen punches him in the ribs, in the same spot as before. Again, the "barely healed" wound from his duel with Lumiya increases the magnitude of the injury.
4) Jacen kicks Luke in the leg, causing "something" to "pop."
5) Jacen drops a steel fixture on Luke's head, knocking him to the ground and breaking his nose.
6) Luke takes another kick to the knee.
7) Jacen tries to strange Luke with another tendril.
So that's two strikes that are only severe because of Luke's prior injuries, and two resulting from Jacen's use of traps that he'd already set up. That leaves three "fair" hits, including the use of the environment in the form of the steel fixture, which is fine.
Now, Jacen:
1) Luke grazes Jacen's kidney with his saber, but Jacen feeds on the pain to make him stronger.
2) Luke hits Jacen with an elbow-smash to the temple that drops him to his knees.
3) Luke knees Jacen in the chin, and hears teeth crack.
4) Luke kicks Jacen in the stomach, lifting him a meter off the deck.
5) Jacen blocks a strike from Luke that packs so much force it drives Jacen's own lightsaber into his shoulder.
6) Luke slashes Jacen across the head, leaving a "palm-sized" hole that reveals bone.
7) Luke hits Jacen in the eye.
8) Luke feints an attack, then Force-pushes Jacen into a tendril-draped rack hard enough that he thinks he broke it.
9) Luke is about to kill him, Ben stops him, Jacen drops the fixture on Luke's head and tries to run away.
10) Luke catches up to Jacen, elbows him in the face, and a bone shatters.
11) Luke elbows Luke in the ribs ("like hitting a permacrete wall"😉 then uses the momentum and the Force to throw himself and Jacen into a wall, with Jacen's skull hitting first.
12) Luke elbows Jacen in the face again.
13) Luke hits Jacen in the same spot with a palm-heel to get distance, and then Ben stabs Jacen.
End fight at that point. Jacen gets seven hits on Luke - two that only mattered because of Luke's still barely-healed wounds, two that he managed because of his tendril things. It was fighting smart, so obviously I won't hold it against him. But Luke had thirteen solid saber/strike hits on Jacen in their duel. As demonstrated, he could've simply ruined him with the Force, but his "battle rage," as Ben called it - plus PIS - clouded his mind. It took both of Ben's interventions, the first where he asks to kill Jacen himself, and the second where he stabs the man, for Luke to calm down and think.
Luke is firmly superior to Jacen in saber combat - he cannot lose to him.