Gamera vs Gyaos (1967)

The 1990s reboot of Gamera made Gyaos something of a signature enemy, with an origin story involving Atlantean biotechnology.  In its original appearance though, Gyaos is ... just some bird/reptile thingy with funky powers.

Also, the 90s version looked much less goofy than this.

Gyaos emerges into Japan when an eruption at Mt Fuji exposes its cave.  It immediately eats a reporter, but is prevented from also snacking on an annoying child when Gamera turns up, attracted by the lava.

Naturally, the two monsters fight.  It's refreshing to see that the producers learned from one of the mistakes of Gamera vs Barugon and got to the kaiju battles a lot earlier in this picture.  If you're feeling generous to Gamera, you might call this encounter a draw: he saves the kid but his arm is badly injured by Gyaos's sonic lance.

Alas, all this kid-saving doubtless means we're heading into the "Gamera, Friend of All Children" period of the franchise.  In other words, the hellish period of the franchise.

The rest of this movie though - apart from annoying kid being annoying and coming up with all the answers while the adults just sit around looking perplexed - is actually not so bad.  I mean, it's not good enough that I'd recommend it to anyone but a kaiju fan, but if you fit that definition then there's a decent mid-movie battle and plenty of the inevitable human efforts coming to naught.