The adventure called "Infestation," pits you and a band of mercenaries against a horde of monsters that serve The Grox. Your captain, along with the mercs, have to fight your way through the Legions of Hell and blow up a huge colony pod that is killing the planet. Bonus points if you are using a melee weapon or even your bare hands.
Killing an Epic Creature in the Creature Stage is no easy feat. Epics are creatures roughly the size of a Kaiju and strong enough to kill you in one hit. It can be accomplished in various ways, but besides the huge bonus, killing it will be something to be proud of, especially if you're alone.
What's better than killing Epics? Siccing them on your enemies!
There are also Epic Creatures in the Cell Stage that can one-hit kill you by swallowing your cell whole. Most if not all of these are usually Carnivores. Despite their danger, you can kill them by using weapon parts (Spike, Poison and Electricity).
Watching the Earth Shattering Kaboom caused by the Planet Buster. Be amazed as the planet explodes and becomes a ball of fire!
The climax of the adventure called "The Temple of Spode" has you protect a group of priests and the titular temple from angry natives for a period of time. After holding the line, the priests' prayers are answered, and lightning blasts apart the natives and their ship. Your Mileage May Vary, though, because you recieve the adventure from the Zealots, the most hated empire in Spore.
The Military Nation's ultimate superweapon in the Civ stage, ICBM, conquers what's left of the other nations by launching a Macross Missile Massacre of NUKES! The only downside is the fallout that it leaves, which makes it impossible to place building on the spots they cover.
And for the Religious Nation, we have a superpower that summons a huge hologram of your creature similar to the ones generated by Religious vehicles, which conquers the remaining enemy cities by...uniting them in prayer? What makes this so awesome is the flashy visual effects that are made up of huge musical scores.
When you finally enter the Galactic Core, you are treated to a cutscene where you travel through a weird, beautiful wormhole, as a deep voice monologues about your accomplishments. This certainly looks like it's building up to a Moment Of Awesome, but when you reach the end of the wormhole...you meet a guy in a little UFO called "Steve." The anticlimactic reveal is more than made up for by the Staff of Life he gives you, which automatically terraforms a planet to T-Score 3, including plants and animals.
The intro cutscene for all adventures show your captain beaming down to the planet while dramatic, courage-inspiring music plays.
The intro to the Cell Stage starts with a comet passing by a solar flare and hurtling towards your chosen homeworld. The comet breaks apart as it enters the planet's atmosphere, and then impacts with a faint crash. You then see a bunch of rocks falling into the ocean, and the last rock to fall in breaks apart to reveal your cell. Complete with perfectly fitting music.
Using the Staff of Life on a dead planet. When the shot impacts, huge lightning storms rage across the surface, followed by a wave of sparkling green energy. When it's over, what was once a barren wasteland is now a lush paradise, teeming with life.
Hell, just terraforming a dead planet to a planetary equivalent of the Garden of Eden in a few minutes is an act of awesomeness by itself.
Some Superpowers in the Space Stage are this. The Scientist's Gravitation Wave produces a huge energy pulse that levels every city on the planet it's used on. The Zealot's Fanatical Frenzy reproduces the religious Superpower from the Civ Stage, causing every city on the planet to convert to your empire.
The Fanatical Frenzy is the most awesome superpower to see in action, too.
There's a Maxis adventure that reenacts Indiana Jones and the Temple of Doom, in which your captain infiltrates a Temple of Doom to snag an artifact called the Golden Llama. You solve some puzzles that have you open doors with jewels scattered around an area, then you cross a rickety rope bridge over a river of lava. Once you take the llama, an Eldritch Abomination breaks through the wall behind it and escape music starts playing. That's your cue to run like hell to the extraction point while evading hordes of monsters.
Wiping out the Grox is particularly impressive, partly because of how much work you have to put into it. It's especially satisfying to hit a Grox planet with the Staff of Life, since life is anathema to them and destroys their settlements instantly.
Starting with a system of four or five planets, all T0, and bringing them all up to T3, with or without the Staff of Life.