Dragon Ball: Raging Blast

Here's a handy list of all the unlockable characters and which battle unlocks them:

Android #16: [Android Saga - Android #16 Makes His Move!]

Android #17: [Android Saga - Android #17 vs The New Piccolo]

Android #18: [Android Saga - Cute and Powerful?! Android #18 Has No Weakness]

Bardock: [Bardock Saga - Frieza's Betrayal! Operation Saiyan Sweep]

Broly: [What-If Stories - Freedom]

Burter: [Frieza Saga - The Comination Attack of Blue and Red]

Captain Ginyu: [Frieza Saga - Confrontation! Captain Ginyu Arrives!]

Goten/Goten Super Saiyan: [Majin Buu Saga - Gohan Amazed! Goten's Explosive Power]

Gotenks/Gotenks Super Sayian/Gotenks Super Sayian 3: [Majin Buu Saga - The Fused Hero is Born! His Name: Gotenks]

Guldo: [Frieza Saga - The Horrifying Ginyu Force! Fearsome Magic, or Just a Trick]

Jeice: [Frieza Saga - The Combination Attack of Blue and Red]

Kid Buu: [Majin Buu Saga - Grab The Future! The Battle of the Universe]

Kid Trunks/Kid Trunks Super Saiyan: [Majin Buu Saga - Vegeta Shocked! Kid Trunks' Explosive Power]

Majin Vegeta: [Majin Buu Saga - Vegeta and Goku's Fateful Confrontation!]

Trunks (Sword)/Trunks (Sword) Super Saiyan: [Android Saga - Hey! Been a While... Goku's Return, and The Mysterious Boy]

Super Gogeta: [What if Stories - Fusion & Porara Part 1: Super Gogeta]

Super Saiyan 3 Broly: [Legendary Super Saiyan Saga - The
Legendary Super Saiyan Reborn]

Super Saiyan 3 Vegeta: [What-If Stories - The Strongest Super Saiyan 3]

Vegeta (Scouter): [Saiyan Saga - Launch It, Krillin! The Hopes of the Spirit Bomb]

Vegito/Super Vegito: [What-If Stories - Fusion & Porara Part 2: Super Vegito]

Videl: [What-If Stories - The Student]