GREAT SIZE
This character can’t be knocked back. When this character makes a close combat attack, it may target characters on higher elevations. This character ignores the effects of hindering terrain, elevated, and outdoor blocking terrain on movement and can move through squares adjacent to and occupied by smaller opposing characters. Smaller characters do not block line of fire to or from this character. This character may draw lines of fire (and have lines of fire drawn to it) as if the character occupied the elevation equal to or greater than the elevation it occupies, using the elevation level with the least restrictive line of fire. Characters with the combat symbol are smaller than those with the combat symbol who are smaller than ones with the symbol. This ability can’t be countered.

Can a Colossal character use Multiattack, ignore [insert power name here], break away automatically, or do something else that isn't in the Colossal Stamina or Great Size descriptions?
Maybe. Many Colossal characters come with their own special rules sheets that detail a lot of extra stuff that they can do or ignore or otherwise change the way they might normally work. However, those rules are not common to all Colossal characers and just because Colossal A can use the Multiattack does not mean that Colossals X, Y, and Z can, too.

Basically, if a Colossal does NOT have its own special rules insert, the Colossal Stamina and Great Size ability is all they can do (barring other special powers and abilities, of course).

Does this ability allow a character to automatically break away?
No. Like the Flight ability, it lets a character that is already moving move through or around opposing characters, but it does not guarantee break away. The character may have some other powers or abilities that allow automatic break away, though.

Also, please note that a character using this ability is only free to move around characters that are smaller. So a character can freely move around characters, but it would still have to stop moving if it became adjacent to an opposing or ; and a would have to stop moving if it became adajcent to an opposing .

If my or is grounded (level 1) and standing next to elevated terrain, can an opposing character on that elevated terrain make a close combat attack against my character?
Normally, no. There are exceptions (like if the opposing character can use Leap/Climb and such), but assuming more or less "normal" conditions, the opposing character is not adjacent to your or so it can't make a close combat attack.

Your character could attack the opposing character, since Great Size specifically says that it can attack characters on higher elevations, but that doesn't mean that the characters are actually adjacent.

Wait, did you say "higher elevations"?
Yes, I did. That is something to watch out for in the 2011 rules: different levels of elevation. Now that we can have more than just "grounded" and "elevated", some game effects specifiy that they only work in one direction (higher or lower) and in this specific case, a character using Great Size can only make close combat attacks against characters on a higher elevation.

So if your is sitting on Level 2, it could make a close combat attack against characters on Level 3 and up, but it could not make a close combat attack against Level 1 (grounded) characters.

Can a or character draw line of fire over blocking or elevated terrain?
Depends on what they are trying to draw line of fire to, so "maybe".

Characters that can use this Great Size ability can draw line of fire to other characters using this same ability at their elevation or higher; whichever offers the least restrictive line of fire. Basically, this means that if there are two grounded characters and there is an area of blocking terrain between them, and #1 wants to attack #2, #1 can draw line of fire from Level 2 (over the blocking terrain at Level 1) and get a clear shot at #2.

Note that this only works between characters that can both use the Great Size ability; if #2 was a regular character, #1 would not be able to draw line of fire over the blocking terrain (and vice versa, #2 could not draw line of fire to #1).