How did you come to that conclusion? This is a genuine question; I'm looking at the stat blocks and I don't see anything popping out at me, so I am curious about what methodology you are using to get a clear picture of their relatively strengths.
He has a full letter grade on Speed, very nearly two full letter grades on Initative
His Combat Perception is 1 Letter Grade worse
His Avoid is almost two Letter Grades higher, his Armor is one Letter Grade lower
His Spiritual Avoid is a Letter Grade Lower, and his Spiritual Armor is two Letter Grades weaker
His Physical Attack is almost a letter grade higher, and his Pen is mediocre.
His Spiritual Attack stats are about a letter grade higher in each case.
The only stats in which the big burning tree actually
beats the Horned Prince is in Combat Perception, Armor, Spiritual Armor, and Penetration.
Meanwhile, the Horned Prince's Avoid is considerably above the Burning Tree's ability to actually
hit him, and even if it tags him anyway, it doesn't do
enough damage to decisively turn the table. Meanwhile, the Horned Prince can evade almost all attacks, will hit him very often, and do a moderate amount of damage with each hit until he wins. If he has Spiritual Attacks, the Burning Tree
cracks like an egg once he brings those out.
On paper, the Horned Prince wins about seven to eight out of every ten fights--only losing if he gets stunlocked somehow and then repeatedly bludgeoned over the head until his distressingly high Health and Qi pool are depleted.
Ling Qi intervening changes this up, because his Perception is relatively weak compared to how powerful his other combat stats are (Meaning she is likely to pull off a OwS Backstab in her opener), but his Spiritual Armor is weak enough that she's likely to have a nigh-all powerful initial opener, and the echo will
wreck his face.
Even if that doesn't finish him off, it means he now
loses nine to ten out of every other fight, and then we have Mist of the Vale to lock him in.
Because you need Perception to escape the Mists, and his Perception is weak.
And that all disregards what kind of mean and unfair things Shen Hu can do to people on the ground. We were told after all that Shen Hu fighting someone ground-bound is a whole 'nother ballgame compared to how he fought us--who scrupulously avoided engaging him on the ground.
And Flight is
hard before Fourth Realm for humans.