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* How about for starters the first level. The return of Green Hill Zone. [[http://www.youtube.com/watch?v=nZzlcI_2adk Classic]] and [[http://www.youtube.com/watch?v=CuqCzlu4rqA Modern]] flavors.
* The glorious return of the song [[spoiler: E.G.G.M.A.N.]] in the Mirror cutscene, and then again outside the Boss gate for [[spoiler:Egg Dragoon]].
* Classic Sonic gets one over his Modern self early on. The game does a fair job in illustrating that rather than having grown superior or inferior over time, Sonic [[spoiler: and Eggman]] have moreso simply ''changed.'' When does this become awesome? When Eggman taunts the Sonics through the door leading to the Death Egg in the post, Modern Sonic decides to run his mouth as he is want to do. Classic Sonic just nuts up and ''goes for it''. For more crowning, whereas Classic Sonic makes it through before the doors close, Modern Sonic [[ButtMonkey just crashes into them like a bug on a windshield]]. In other words, ''he was faster''.
* The return of the G.U.N. military truck. [[spoiler:This time it is equipped with giant saws and rocket boosters.]]
* [[spoiler:TheReveal that although up to this point in nearly every 3D Sonic game, Eggman got his ass kicked by the game's EldritchAbomination, who went crazy and/or assumed itself as the BiggerBad, not only was he able to somewhat control the Time Eater just by himself but, with the help of his past self, he turned it into a pilotable mecha!]] Talk about TookALevelInBadass.
** The very fact [[spoiler: Eggman while using]] Time Eater starts the game turning nearly the entire hero cast into statues. Just one cutscene into the game and he has neutralised almost all his foes except Sonic.
* Defeating the Time Eater [[spoiler:and both Eggmen]], proves both Sonics to be badass.
* Shadow's rival boss fight, in which you [[spoiler:race for possession of power cores floating around the ARK. If Shadow gets two cores, he attacks you with multiple Chaos Spears and a blast of Chaos Control, accompanied by ''All Hail Shadow''. If Sonic gets two, you need to smash meteors into Shadow whilst ''Live and Learn'' plays. The game appears to make a point of showing that Shadow matches Sonic point-for-point, too; he runs at almost exactly the same speed, and both characters will deflect away from each other if they get too close in Boost mode.]]
** Remember the fight with Silver in ''VideoGame/SonicTheHedgehog2006'' where it was freaking awful in every way? Well, you are going to love this one; No sarcasm! [[spoiler:Silver does a much better job of putting across how powerful he is than any other game so far has, using his psychokinesis to its full extent. He throws multiple vehicles and various hunks of debris at you for most of the duration of the fight, fires the occasional psychic energy knife, and then tops it all off by chasing you down with a ''massive'' ball of twisted metal and debris, which Sonic can just barely keep ahead of. And he ''still'' throws other stuff at you during this!]]
*** What's more awesome than that, though? [[spoiler:After the first time you beat him, any time you go back to the fight, [[JustForFun the two are just doing this for fun]].]]
* The new version of the [[spoiler:Perfect Chaos fight is this in general, as well as specifically for Sonic himself. He no longer needs to be Super to defeat the creature, and rather than fly across the flood-water, he simply hydroplanes across it by running at supersonic speeds. There's also that pretty sweet mix of ''Open Your Heart'' that plays for most of the battle.]]
** [[spoiler: Chaos, rather than just blasting raw power, is more cerebral this time round, blocking Sonic's way with loads of maze like pathways and obstacles, proving despite his role as an angry rampaging beast, he can test Sonic's brain as well.]]
* Seeing both Sonics go [[spoiler:Super Sonic at the same time, set to the insanely upbeat music from Sonic 4, like a happier DBZ.]]
** [[spoiler:The BadassBoast Sonic gives is a nice touch on top of that. "Time to scramble some Eggmen, SUPER SONIC STYLE!"]]
* Classic Sonic ''punting'' Metal Sonic into the sky at the end of their duel.
* [[BestLevelEver Rooftop Run Act 2]]. Off the heels of a really hard level, check. Glorious music, check. Fast pace with enough challenges to remain fun, check. Rail grind that gives a view from hundreds of feet in air and then has you dive back into the town... check.
* Crisis City. Given how [[VideoGame/SonicTheHedgehog2006 the game it came from]] gets a ton of crap due to [[ObviousBeta how rushed and buggy it was]], it's awesome to see something from that game redeemed by having a fully developed and awesome game take a crack at it. They also made the music in both levels ''even better'' than in the 2006 game, and the music was one of it's redeeming features as it is.
** They even manage to ''troll you'' and make it ''enjoyable'' in Classic.
** Modern's level is also a great example of a level that is challenging, but not in a cheap way.
* And an oft-overlooked one from the 3DS version. [[spoiler:Right after both Sonic's and Tails' find the Time Eater, what to the Tailses do? They attack him head on, no questions asked! Sure, they failed, but their efforts caused the Chaos Emeralds to radiate with energy so the Sonics could transform into Super Sonic!]]
** [[spoiler:And they fare better than the two Sonics did before going Super anyway!]]
* Modern Sonic is more of a badass than ever, as the ending cutscene/clip to the [[spoiler:Egg Dragoon]] boss fight will show you.
* [[PlayingWithATrope Played with]] after beating the [[spoiler:Death Egg Robot]]. Classic Sonic does a badass pose [[UnflinchingWalk after landing]] but gets scared by the ensuing explosion.
* The Death Egg Robot's entrance is pretty awesome.
* Sonic running down a REALLY tall building in Speed Highway, complete with a herd of Speeders chasing after him, and accompanied with the "Goin' Down" music playing.
** Some of the shortcuts in that level also require jumping onto a random helicopter flying above you, and getting back onto a rocket that Sonic just jumped off, making this one for the players too if they can succeed.
* [[{{Determinator}} Classic Sonic traversing the Crisis City tornado, just to get his goal post back.]]
* Eggmen [[spoiler:smashing both Sonics]] prior to the final fight.
* Your favourite Sonic music piece not in the Custom Music list in the game? For the [=PS3=] version at least you can use the in-game XMB to play music from there, a feature that next to no [=PS3=] game actually supports.
* [[spoiler:Unlocking Super Sonic as a skill!]] While it was first reintroduced for SonicColors, this game pushes Modern Sonic's use of the skill UpToEleven! Now, in addition to normal bonuses [[spoiler:Sonic's able to use a flight power similar to Chaos Control to tear through levels carefree. Watching him blast through what were previously incredibly difficult areas is absolutely awesome!]]
* Classic and Modern Sonic's ranking animations [[spoiler:while super]] are unbelievably badass, with nearly all of them being nods to poses and motions they've used in previous games.
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