When the Colossus Titan shifter transforms, it generates a large explosion which can be used to kill their enemies. How large is this explosion supposed to be? Is there any info about this?
It actually varies, since bertholt had quite precise control over it.
When he transformed into the Collosal titan (partial transformation though), over the wall at Trost, his transformation only caused a wind blast who knocked some trainees over the Wall.
Then at the return at Shiganshina, he transformed mid air, with the explosion being comparable to a nuclear weapon, also releasing smoke cloud high up in the air. (But as it seems, he still could have done an EVEN MORE EXPLOSIVE, but he could fight well, and had enough mass thereafter too)
During the retake of Shiganshina, Bertolt releases a similar amount of energy to a small nuclear device, creating a mushroom cloud of dust and rubble, and also ravaging part of the district and killing a great number of Survey Corps members.
- In control of Armin, the explosion during the transformation at the PORT was enough to blast off the naval port at Marley.
So far till now, the explosion is comparable to a small nuclear bomb, though if intended only a single transformation, more explosive transformation may take place, this is upto speculation.
NOW, A MAJOR SPOILER FROM MANGA
To this, armin also agrees that this may be the only way to defeat eren's founding titan, if they can't come to terms with talking, and considering they also talked about different place eren maybe using the war hammer, armin should have had good estimate, how much area he can blow, which for blowing up most/all of eren's titan will be a COLLOSAL EXPLOSION.