Whether in games, comics, anime, etc, there are a myriad of power ups characters can use in order to beat a villain or just become stronger in general… Let’s discuss some of them
Note: As long as they transform or get a power boost/special ability it counts
EDIT: Fusions count
force unleashed 2 unleashed mode is pretty great
It’s a transformation.
It counts.
Metal blade anyone?
Cheesy I know, but still one of the better Transformations I’ve seen;
Nuva, Hordika, Mahri, Phantoka/Mistika, Tahu’s golden armor…Bionicle was pretty deus ex machina-y, usually in order to sell sets.
The worst one, though, is probably the ultimate deus ex, the One Ring. I give it a pass for being the king of all deus exes though.
Super Mushroom.
Mega Mushroom for the win, dude.
This and the ensuing battle are some of the best Ninjago scenes ever.
Megatron -> Galvatron in the 1986 Transformers Movie. That was pretty cool.
My personal favourite transformations:
One of the best KR final form debuts ever.
Makes much more sense one you watch the series, but still cool without seeing it.
The Brain Attack monster’s transformations were pretty rad. I loved how each of them actually took elements of their individual environments during their transformations…
Like Scarox transforming inside of a sand tornado…
…Ogrum being engulfed in vines and swamp gas…
…Bruizer absorbing surrounding rocks…
That accually made me really sad. He looked so happy. Just walkin’ around, eating rocks 
‘Nuff fraggin’ said.
any of Sonic’s many forms
Obviously one of my favourite transformations, Fierce Diety Link from Majora’s Mask
SO, OP! 
I personally found some of those incredibly stupid and unrealistic (like how a bunch of stones just surrounded Bruizer), but each to his own
Super Saiyan.
RIP Krillin
to this 