A Big Figure is basically a big sized LEGO minifigure, normally with no points of movement and no customisation. This means that we cannot swap heads, torso or legs.
The first Big figure was released with the set Lego 4950: The Loader-Dozer in 1999 from the ROCK RAIDERS theme. The first Big figure was a Rock Monster, a figure that only moved the right arm.
We then had to wait 8 years until the next big figure was release in 2007. The big figure was a Giant Troll from the set Lego 7036: Dwarves’ Mine.
Several variations of this Troll were made, 5 to be exact, all between 2007 and 2009.
In 2009, in a upgrade to the ROCK RAIDERS theme, the Power Miners, 3 new big figures were made. They were called Geolix, Tremorox and Eruptor. These big figures were different from the previous because they had a translucid body.
Next in line were several big figures from IPs that Lego acquired over the years like Star Wars, Marvel, DC, TMNT, Moana, Harry Potter and Lord of the rings. In the list are big figures like Wampa (Star Wars), Cave Troll (LOTR), Goblin King (LOTR), Rancor (Star Wars), Green Goblin (Marvel), Darkseid (DC), Gorilla Grodd (DC), Thanos (Marvel), Killer Croc (DC), Hulk (Marvel), Red Hulk (Marvel), Dogpound (TMNT), Leatherhead (TMNT), Troll (Harry Potter) and Maui (Moana).
From all of the previous, most of them shared the same body although there were some exceptions like Dogpound (TMNT) and Harry Potter’s Troll that had a minifigure head and a full one piece custom body with something that is not common in a LEGO figure: clothes.
From the LEGO brands there were only 2 more Big Figures: Dogshank (Ninjago) and Mungus (Chima).
In resume, almost all the latest big figures that LEGO released share the same base (excluding a couple of exceptions): fixed torso with custom fixed head, removable arms and fixed legs in the same position walking position.
It’s and interesting type of figure, but the lack of customisation and movement makes it an uninteresting piece of LEGO. I would prefer a big size version of a minifigure where we could change the head, torso and legs and interchange parts. But, for most of these figures, it’s the only representation of them in the LEGO world, so they basically a need to have.