@Background Pony #46B8  
The updated chart has Dragon Lord Torch, the Ursa Major and the Alicorn Tantabus surpassing it more than twice over.

Welp, i guess the Hydra is the tallest one.

@GundamAlicon3.0  
Or Kronos. Or Godzilla.

Tirek’s that big?,  
Better send Metroplex

@Glimmy-Glam  
It must be even worse than Gensokyo. That’s taking into account those portals, too.

@Markiz93  
Man…Equestria is SCARY!

@Cirrus Light  
Done:

@Markiz93  
Oooooh! Coolio! Keep me posted, I want to throw in some stuff when you’re done :p

Well, I’m going to make the biggest size comparison with almost all creatures from the show, and one from Rainbow Rocks (siren). It will be based on this chart.

@Spiked Punch  
Attack on Equestria.
 
Oh gosh no. Too many character deaths >.<

@Glimmy-Glam  
And I believe Torch was equal/larger than the Ursa Major.  
Equestria has its share of Kaiju it seems.

@Cirrus Light  
Reversal of the food chain would be pretty painful. Everyone’d start to rot from the inside as the bacteria they consume (after said bacteria processed the food) start eating them instead and immune system is not ready.

@Barhandar  
I misread that as “How casense is plankton filled by whales?”
 
IT’S A REVERSAL OF THE FOOD CHAIN!
 
The plankton have risen up against their enemies.

And the Ursa Major would be too big for this chart. :P

@Barhandar  
Of the top of my head, I’d say “pretty darn”.

@Background Pony #6136  
How calorie-dense is the plankton filtered by whales?

@Barhandar  
It’s not the matter of quantity, it’s the matter of “density” of nutrimental value. If nutrimental value is low, then they simply won’t have time to eat “plentiful” food: they will starve while eating, because nutriments lost is higher than nutriments gained.

@Background Pony #2335  
@DragonWraith  
These species of reptile and fish die when they can no longer obtain the food their body needs (overgrew the supply or became too ponderous to catch it) - they can’t die of old age. Now, dragons in FiM eat gems, and gems in Equestria are so plentiful, their caves look like modern supermarket food aisles.
 
Any dragon that can out-compete other dragons will therefore grow as large, or larger, as Torch. And given Spike has ponies’ support (when he’s not being a chew toy, that is). Pretty sure distant future of FiM is destined to have the Dragon Lord Spykoran the Great.
 
P.S. Herbivorous mammals also die by starvation and predator, not old age, but it’s not because they cannot like fish, it’s because their teeth wear out and render them unable to feed before they succumb to age. You can rub this into any aggressive vegan’s face, because death by starvation or predator’s teeth is far crueler than death by butcher’s blade, and therefore all “HURR DURR NATURAL HURR DURR NO BUTCHERING NO FARMS” vegans are committing animal cruelty or hypocrisy.

@Background Pony #2335  
Most species of reptile and fish never stop growing. Dragons are probably similar, being at least distantly related to reptiles.  
Torch is probably really old, even for a dragon.

In Gauntlet of Fire however, we saw that Torch was clearly waaaay bigger than any other dragon we’ve seen in the show. He was closer to the Ursa Major in size than to other dragons, since his head alone looked the size of the Ursa Minor. This means that unlike other creatures, there’s not a “set” standard for a dragon’s size. Some can apparently grow many times larger than others. Whether this is defined by chance/genes or something else, we don’t know.

@Barhandar  
Black hole cosmology is actually something I’ve spent the last few years researching at my own level :p

@Cirrus Light  
And since university-mass black hole is going to have density less than Earth’s atmosphere, and we have no idea what happens inside black holes and whether do they have density variations, some crack hypotheses exist that postulate our entire universe is actually a (really fucking) large black hole.

@Blissey1  
The funny thing is, because their mass is linear, it varies. The Swarzchild radius is
 
r = 2GM / c ²
 
=>
 
M = r c ² / 2G
 
The volume of a sphere of radius r is
 
V = 4 pi r ³ / 3
 
Thus the density is
 
M/V = p = 3 r c ² / ( 8 pi G r ³ )  
= 3 c ² / ( 8 pi G r ² )
 
Or in terms of mass instead of volume,
 
p = 3 c ² / ( 8 pi G ( 4 G ² M ² / c ⁴ ) )  
= 3 c ⁶ / ( 32 pi G ³ M ² )
 
So bigger black holes are actually less dense. It leads to an interesting phenomenon… A solar mass black hole is only a few km.
 
But, supermassive black holes can be as large as entire freaking star systems.
 
The one in the center of our galaxy, Sagittarius A, has a mass of ~1.4 million solar masses.
 
A solar mass is %2e30 kg, so that’s 2.8e36 = % 3e36 kg.
 
c = ~3e8 m/s,  
G = ~6.67e-11,
 
r = 2GM / c ²  
= 4e9 meters
 
The radius of the sun is ~0.7e9 meters.
 
An astronomical unit is ~150e9 meters (distance from Earth to sun). So a hundred-million solar mass black hole (and they exist) would have a horizon the size of a solar system.
 
Never mind the accretion disk.
 
But most black holes are only a few km.
 

 
…it should be noted, though, that actual black hole geometry is a lot more complex because of curved spacetime. The “r” in these equations refers to “reduced circumference,” the radius deduced by going in a circle around the object and dividing that circumference by 2 pi.
 
Actually traveling radially inward, the distance you record will depend on how fast you let yourself fall, due to relativistic effects, so the “real” volume is more nuanced, depending on what you mean by “real.”

Needs Full-powered Tirek, Greed!Spike, Ursa Major, and Torch.