This form is the ordinary Super Saiyan form of the legendary Saiyan. It is seemingly identical to the Super Saiyan form, though is of a different evolution. In addition, in this form Broly is powerful enough to defeat both Goten and Trunks as Super Saiyans at the same time, and is able to outmatch base Gohan, despite Gohan having powered up considerably since his battle with Cell, though base Gohan is able to hold his own. Upon seeing Gohan turn Super Saiyan 2, Broly responded by taking on his Legendary Super Saiyan form.
The form also is shown to be exceptionally fast, being able to move as if teleporting, which is especially evident by how Broly managed to get the drop on Goten and Trunks shortly after using Planet Geyser. However, the form has its limitations: using any particularly devastating attacks, such as Planet Geyser, carries the risk of harming the user unless they are protected beforehand by an energy shield.
A user of this form cannot maintain the form while they are either in a coma or otherwise asleep unlike the Super Saiyan Full Power state, which is especially evident in Paragus's flashback to his outfitting the crown onto Broly, and later when Broly fell into a coma seven years prior. It is also noted that the legendary Saiyan is born Super Saiyan. Aside from the standard gold hair, it also has various different hair colors depending the lighting, including auburn as well as pink/purple and lime green.
Broly utilizes this form in flashbacks of Dragon Ball Z: Broly - The Legendary Super Saiyan, when becoming enraged at the appearance and mention of Kakarot he proceeds to transform from A-type Super Saiyan into C-type Super Saiyan (with green hair) - back to A-type Super Saiyan - and then into Legendary Super Saiyan.
Upon arriving on Earth in Dragon Ball Z: Broly - Second Coming, Broly transforms into this form, he utilizes it in his battles with Videl, Goten, Trunks and Gohan until Gohan becomes a Super Saiyan 2, and thus Broly responds by becoming a Legendary Super Saiyan.