Not much power to this thing. It's hot enough to cause a forest fire and hurt a giant human but nothing much else. In fact it's lacking in so much to kill a fellow monster that it seems it's more just a defensive weapon then an offensive one. Baragon was able to spam it like King Ghidorah so it seems that it's meant to burn an attacker as quickly and as many times as possible to make them back off.
A pretty cool concept and it explains how this dinosaur survived underground for so long, he had this niffty power to help him see in the dark to hunt for food. This could actually be useful in combat if combined with his digging ability as he could use his horn to get an attacker to look at one spot while he quickly digs a tunnel behind them to ambush them.
With the invention of the Type 66 Maser mankind was no longer helpless against giant monster attacks. These powerful streams of energy are capable of killing monsters like Gaira and making some more durable critters like Gigan and Megalon actually fall down and crawl behind trees for cover. At long last man had a weapon that could kill a monster or make it retreat. They even make King Ghidorah, one of if not the most durable monsters ever flinch. Were it not the vehicles frail nature these burning energy rays could make even Hedorah retreat if you kept it up for a day.
Kumonga's most deadly weapon, if unable to take down a monster with one shot because it's biology &/or size is different then it's normal pray (Kamacuras) he can fire several more to inject even more poison into his target. Even worse it can take out an eye as Godzilla learned the hard way. This combined with it's ability to shoot web fast enough to actually beam clash with Godzilla's Atomic Breath(!) makes for a deadly combo in the spider's arsenal as he can quickly immobilize a fellow monster and finish it off. Were it not for Minlla Godzilla would have died and the King of the Monsters would have just been a meal.