This is a list of all possible Nemeses you can encounter in Norende Village.
The weaker form of Belphegor fights much like his normal self, but with stats adjusted for lower level parties and a smaller movepool. Just like the normal Belphegor, Belphegor [-] is immune to every attack except his elemental weakness, and he will be healed when hit with any attack he isn't weak to. Striking him with said elemental weakness will cause it to change, and he will cycle between Water, Lightning and Fire weaknesses each time he is hit. Belphegor still has Hammer and Diffusion Ray for single-target and whole party attacks, but he only has the Firaja spell. He can also use Summon Spheres as well, the Spheres sharing his virtual damage immunity. The Spheres can use Body Slam to attack and will Self-Destruct after enough turns have passed.
This walkthrough assumes you're challenging Belphegor with an early-game party. The only jobs that can damage Belphegor at this point are likely Black Mages and Spell Fencers. As with the real Belphegor, using the Freelancer's Examine ability will show you which elemental weakness he is currently weak to throughout the battle. Belphegor is a lot more manageable without Sloth and his other spells, so your main concern is his Firaja, which can be nullified by timely Defaulting and group heals. When the Spheres are summoned, focus on clearing them before they self-destruct. Group cast Black Magic is good for hitting all of them, as well as combat items if you've built the shop in Norende. Keep casting Belphegor's weakness and defend against his periodic Firaja and you should beat this Nemeses without much trouble.