First, Future Gohan strikes a fighting pose as he charges at the opponent and kicks them up into the air. Then, he flies up past the opponent and flies back to roundhouse and punch them away. Next, he grabs the opponent by their ankle and shouts "Die!" as he flies downward to slam them into the ground. Finally, Future Gohan backflips away and shouts "Watch it!" as he fires the powerful One-Handed Kamehameha mk.II at the opponent, inflicting a high amount of damage.
Future Gohan used part of this attack during his battles against Future Android 17 and Future Android 18 in Dragon Ball Z: The History of Trunks. When exchanging blows with 17 in their first battle, Future Gohan gained the upper hand and attacked with the Fierce Combination rush's kick, kicking the Android onto a railing. In his second and final battle, Future Gohan overpowered 17 and 18 in a Energy Clash with the Fierce Combination rush's one-handed Kamehameha, blasting them across the ground. Future Gohan later attacked 18 with the Fierce Combination rush's ankle-clutch slam, driving the Android through a damaged building.
Video Game Appearances
This technique was originally known by its Japanese name, Gekiretsu Ranbu, in Dragon Ball Z: Budokai Tenkaichi 3, where it appears as Future Gohan's Ultimate Blast in his Super Saiyan form. It was named Fierce Combination in Dragon Ball: Raging Blast 2.
In Dragon Ball Xenoverse 2, the part which Future Gohan is carring his opponent to the ground is used as his grab/throw while the Kamehameha finishing blast appears as an Ultimate Skill called One-Handed Kamehameha mk.II.