Alright, let's start with the most important thing in my opinion: his hand and tail.
Pictured: Ridley's hand.
Pictured: Ridley's tail. (Estimated)
Because these shadows are on a wall, the only thing that can distort it is a zoom in effect on the picture. But since the shadows mostly stay true to the size of the characters, these are at least 80% accurate to actual size, in my opinion.
And it took me a while, but I found a another character shadow on the pillar, Donkey Kong.
At 2:29, look at the pillar, slow down the video, and don't blink.
That's my estimate, but I'm probably off on the fill in, so keep that in mind.
Ridley's tail is no where near Donkey Kong's height. It is most likely only 1/2 ish of Donkey Kong's height.
and his hand is only 1/6 of Donkey Kong's height.
Onto the hand!
Picture A: Ridley's size in Other M.
Picture B: angel glory's resized Ridley holding Samus.
Judging by the hand picture, if we increase the size of the hand shadow by a few knuckles, doing so would most likely yield Ridley's size from Picture B.
As for his tail, it's most likely this size:
Left: This is the size of Ridley's tail in Other M as compared to Samus.
Right: This is the estimated size of Ridley's tail in Sm4sh as compared to Pikachu.
Credit to @
Dalek_Kolt for this
Assuming the blob above is Pikachu, roughly six Ridley tails can fit inside Pikachu.
Therefore, Ridley's range of sizes are these, hardly boss-sized.
Ridley's largest size:
Ridley's smallest size:
Size comparison with Bigley and Smalley:
Bonus Yellow Devil comparison.