Wha? Aren't Monster X and Keizer Ghidorah the same being?
Well, besides that point.
1. Ultraman Belial (He took on an army of Ultras, survived a crash course from one planet to another and was still as good as new, intelligent, powerful and extremely durable etc)
2. Godzilla GFW/With Kaiser Powers (Pretty much a more aggressive yet powerful updated take of the Showa Godzilla)
3. DesGhidorah (Seemingly Immortal, extremely powerful, can causing the ground to split open and release flames from the earth itself. A perfect move that can help take out the base completely)
4. Legion (A semi-powerful tank and with her swarm she'll provide good results)
5. Armor Mothra (Air Support, and a Dogora-killer)
Godzilla and Belial head out and attack the main powerful enemies(SG, SMG, GKG, and MX/KG), while having most of the focus place on them, Legion unleashes her swarm to cause multiple diversions and help Godzilla and Belial while she digs around and takes out the base's mechanical defenses. Armor Mothra takes out Dogora then aids in taking out the rest of any kaiju remaining. While Desghidorah aids Legion, focusing it's power and energy in crumbling the headquarters by opening up the earth and unleashing hellish flames in order to break down their structure and destroy it.