Daijinryu is likely the largest Mecha in the franchise, but don't misconstrue size for power! Kyukyoku Daizyujin, in a special Dino Super Video or something like that, was stated as having an incalculable power. Magiranger didn't use overly Giant Mecha, but it did have Near-Daijinryu-sized characters, making them comparable to a strong Mecha. In Boukenger 21, the Precious of that episode was used to enlarge Ultimate Daibouken, making it possibly the strongest for a brief period. The Rocket Drill GoBuster-Oh stopped the Big Machine in the first Taisen crossover. GaoKing and DaiVoyager received massive power-ups in their individual VS. with Super Sentai!

Except Daijinryu is more than 10 times the size of every sentai's main mecha. We only seen a tiny part of his power and is devastating. He even have other powers like hypnotizing humans to commit mass suicide. I don't think any Final Cluster Mecha like Ha-oh Shurikenjin can stop him.

Wait I thought mecha meant the robots that they pilot. If it does then Daijinryu should not count.

Daijinryuu has scary powers. He has important role in Dairanger story. I remember he can destroy one of Gorma monster just with Daijinryuu's foot.

But the Daijinryuu in Power Rangers Counterpart (Lord Zedd's Serpentera) looks very very boring because Serpentera is need more fuel like normal vehicles and Serpentera is destroyed by Cole (Wild Force Red Ranger) when Cole was riding on his new motorcycle in Forever Red Episode.

Wild Force Serpentera is a lot smaller than the original. I wish they summon their megazords and combine their power like those crossover VS episodes, but I guess they ran out of budget by getting all the red rangers together.

"Mecha" has become a very loose term in Sentai. Daizyujin, Daijinryu, Muteki Shogun, and others are considered "Mecha" even though they are technically alive. Daijinryu counts cause he isn't any different from the armored nature of Dairenoh or Won Tiger. Plus, they made a figure!

Certain types might get close. We also don't know exactly what Daijinryu's temperament would be. If he fought someone like Daizyujin, he might back off cause of their "divinity". A built Mecha might just get scrapped, but a challenge would still be attempted. It's curious why Daijinryu made no appearance in Gokaiger? Wouldn't the Great Legend War have been too noisy? He couldn't have been overwhelmed, right?

Simple. The Toei Tokusatsu Universe basically told Daijinryu to chill and watch how they deal with each other alongside some popcorn.

Maybe Daijinryu became more mad about the extensive usage of qi and you power rather than just fighting alone, if that might make more sense continuity-wise.

He's either sleeping or forgot to check his notification. The Great Legend War ended pretty quickly, so maybe he knew and retreated after seeing the aftermath.