The Omega Blaster is the Legendary Super Saiyan Broly's most powerful attack that he used in Broly: Second Coming. When Broly uses it, it changes from a small energy sphere into an enormous energy bomb of devastatingly great power. Not only can he control the size and speed of this attack, but he can also power it up by launching ki blasts into it to push it forward, making it even more powerful and destructive enough to destroy the whole galaxy.
Broly tried to use it as a final bid to destroy the Earth, however Goku, Gohan, and Goten counterattacked with the Family Kamehameha. As Broly keeps powering up his attack, Trunks launches his ki blast at Broly's energy ball to form a barrier. This stops Broly from powering up his blast, causing it weaken and decrease in size. Goku, Gohan, and Goten then launch all their power into the Family Kamehameha, which breaks through the Omega Blaster. Broly tries to stop the attack, but fails as the blast sends him into the sun where he is presumably disintegrated.
The attack was named in the Budokai Tenakichi series as Broly's Ultimate Blast, however, unlike the other ultimate blasts in Budokai Tenkaichi 3, it is absolutely unblockable. When using the Omega Blaster, Broly shouts "Struggle all you want, in the end you're still dead!"
The technique is named Gigantic Meteor in Dragon Ball Z: Budokai 3, in the Dragon Ball Z: Shin Budokai series, and again most recently in Dragon Ball Z: Burst Limit and Dragon Ball Z: Infinite World. Broly creates a ki-sphere in his hand. He charges at his foe while he laughs, hitting his enemy with it. He continues, beating up his victim using only his hands. After this, he grabs his victim's head, smashing him or her to the ground. Broly creates another ki-sphere and backs away, laughing again, as the sphere gets larger and more potent. Finally, Broly shoots the Gigantic Meteor, and his foe attempts to hold back the move. The Gigantic Meteor grows larger, resulting in a huge explosion that blows up a planet.