Better Than Canon: A handful of Dream Mode endings from the first game are considered this, but Toki's, Jagi's, and Rei's in particular stand out.
Broken Base: The two games are different enough from each other that playing them can give you completely different opinions, and thus, completely different fanbases. The first had a skill point system with you unlocking abilities on a huge tree, while the second had a system based on random drops where you never had to think about what you were doing. The first had English dubbing, the second didn't. The first had a tighter, more edited version of the story, the second had every single last story bit, often told in cost-cutting freeze-frames (which was cool or cheap, depending on how you looked at it). Ultimately, it's a push and down to personal preference which you liked better.
Ensemble Darkhorse: Heart strikes again; he beat Juza and Fudoh out as a playable character in the first game's DLC.
Even Better Sequel/Surprisingly Improved Sequel: From the point of view of story coverage and number of playable characters, Ken's Rage 2 is RIDICULOUSLY better than the first game. The first game was basically the Cliff's Notes version of the first saga of the manga(the Hokuto Brothers saga), barely covering the main story and with only 10 playable characters. The second game follows the manga so religiously you can actually play it instead of reading it or watching the anime and get the entire story; it covers both the Hokuto Brothers AND Land of Shura arcs; and raises the character count to 25, including all the Nanto Rokuseiken, the two main Goshasei(Fudoh and Jyuza), Adult Bat and Rin, Falco, Ein and the Rashos/Hokuto Ryuken fighters.
Game-Breaker: Raoh overall, most of his attacks hit in an area his strong combos hit in wide areas, does more damage than any other character even when everyone has max stats.
Toki also qualifies for his R1/RT special which parries any attack and counters, with a high chance to inflict meridian shock, in the western release its properties are slightly changed to make him FULLY invincible while doing so(even if you dont parry an attack) as apposed to only being invincible if it parried an attack. arguably makes him the easiest character to do boss rush missions at first.
Kenshiro is one surprisingly, mostly considered to be average overall in comparison to the rest of the cast, most overlook the fact he possesses an infinite loop combo, by grabbing your target and pummeling him with the Square Grab you can go into the Triangle strong throw,and here's where the game breaking comes in, you can cancel the kick with Ken's R1(the backdash, rolling in any other direction won't work) and immediately follow up with a normal combo again and cancel the second punch into his throw again and repeat the process until you screw up or the opponent is dead.
With some attack boosts and the projectile-powering skill, Mamiya's crossbow can one-hit kill entire squads of mooks, and repeatedly knock bosses around until they die.
Tear Jerker: The final day of Rei's life is every bit as tragic as it was in the Manga/Anime, but it's made even more upsetting with Accepted Fate, a very solemn piano piece. The sequel takes a more subdued route and has no soundtrack, which emphasizes the tragedy in a more subtle way.
Toki's Dream Mode ending in the first game. He dismisses the visions as a fever dream rather than a possible future, and thus he just sits and waits for death to come.
That One Attack: Raoh's energy blasts. However, they are as overpowered in the players hands as they are in the computer's, although the computer can skip the basic combo strings and use them at will.
That One Boss: Raoh at the end of Kenshiro's Legend Mode, you will need Musou Tensei for the first time you do that fight, you won't win otherwise. Kenshiro is also this to Raoh to a slightly lesser extent in his legend mode.
If you activate the Harbinger Of Death bonus, Amiba becomes a particularly unforgiving fight in Mamiya's Legend Mode.
Harbinger of Death tends to do this to almost every boss, more so with major characters who can and will use their level 3 Hyper signature moves. if you're not playing as Ken, Rei, Toki or Raoh you stand a very good chance of being hit, taking a ton of damage and being left in spirit or meridian shock.
Good lord, Toki in the DLC challenge mission Four Hero Rumble, after fighting through Ryuuga, Fudo, and Juza, you then have to fight Toki, who if you let him put you into Meridian Shock, are dead. Here's why: He inflicts every meridian shock status in the game, you're poisoned, cant use Signature Moves, you take even more damage than you normally would in shock, cant block any attacks at all, and to top its duration is extended beyond the normal time it lasts normally.
Unexpected Character: It was a given that adult Rin would be prominently featured in the story mode of the sequel. It was much less of a given that she'd be a fully playable character.
Win the Crowd: Koei had a tendency to tone down the violence in their international releases of Dynasty Warriors games, so a handful of Fist Of The North Star fans were skeptical. When the first trailer showed enemies exploding into bloody giblets, it won them over.
Even better for western audiences is that the game became more violent as a Regional Bonus.