We all know (At least those of us who are Dragonball Z fans) of the movie Broly: The Legendary Super Saiyan.
In this movie a saiyan survivor named Broly along with his father Paragus trick Vegeta, Future Trunks, Gohan, and Goku to a new planet they have dubbed New Vegeta. Along with them comes Piccolo and a few others.
During the fight Broly takes down all but Goku whom they have the final battle with. He uses the combined forces of his allies and uses an energy punch that seemingly kills Broly (We find out later it did not)
However, one thing always bugged me about the ending. It was a cope-out they used the power of friendship to defeat a foe who was throughout the runtime depicted as leagues outside their ability to fight.
Now first a little something. An aside about Super Saiyans
Super Saiyans all kinda look the same (Except three and four and now God but still) So some don't know the different
SSJ1 (Basic Super Saiyan, this form increases the fighter by x100 their base abilities)(Akira Toriyama has stated this)
ASSJ (Ascended Super Saiyan this form is vastly superior in strength and power over SSJ1. The proof of this is in the fights against Android 18 and Semi-Perfect Cell. When fighting 18 two SSJ1 fighters where not able to make a single damaging blow and she was able to literally shatter ones arm with a simple kick showing she was far superior. However, after Cell absorbed 17 who is on par with 18 in power ASSJ manhandled Semi-Perfect Cell with minor effort as Vegeta in ASSJ was toying with him. This means that ASSJ is easily three to five times as strong as a SSJ as Semi-Perfect Cell has no trouble stomping Piccolo who was even stronger then a basic SSJ1)
[An Aside about this involving Broly. Vegeta in Super Saiyan form (We cannot 100% confirm this is ASSJ but it is likely) kicks a Suppressed Super Saiyan Broly (Broly is restrained by a device putting him under his fathers control) this kick does absolutely nothing to Broly who is not yet in normal SSJ1 form.]
Check out moment 3:28 to see it fully
USSJ (Ultra Super Saiyan, this form allows a Saiyan to increase their power and physical strength to levels that could at least in part hurt Perfect Cell. However it comes at the cost of their speed, making them nearly half as slow as their previous ASSJ form)
Full-Power SSJ (Full Power Super Saiyan, this form is considered full mastery of the Super Saiyan form, coming from staying in it constantly and not requiring the user to power up. In the movie Goku and Gohan break this form but are still able to reach the same power as they have spent weeks if not months at this point in this form during the Cell Games (They where in the HBTC, hence so long) This form is strong enough to fight with Cell on even terms for an extended period of time, as we see Goku perform during his fight with Cells days after this fight would have taken place. Showing it is easily on par with Cell but not superior)
Of course SSJ2 is superior to all those forms making a dramatic increase in speed and strength and is considered twice as strong as SSJ1 however, this I believe is under the assumption of twice as strong as FPSSJ1 not standard first transformation SSJ1
Now with that lesson over the fight can begin.
Broly at LSSJ (His own unique form of Super Saiyan)
SSJ2 Gohan (Cell Saga)
SSJ2 Goku (Beginning of Buu)
SSJ2 Vegeta (Majin)
SSJ2 Trunks (I know he never reached it but we can base it off Gohans)
and Full Power Piccolo.
The battle takes place as it did in the movie, same location and rules. No BFR and Broly is Bloodlusted.
Also to be sure there are no Sensu Beans on the planet and they have a time crunch of 15 mins before the comet blows the world up.