I felt the final battle after the epic saving of all dimensions was an appropriate denoument that brought the fight to being something personal.
But did it really need to have a house flying all over the place? Come on. Sometimes I feel Amemiya and Co. forget it's a TV show and not a video game. Sometimes it can work, but in this case... and we just had a climactic battle between Red Mask and Garo, and a personal confrontation between Leo and Sigma. This was pointless. I almost chuckled at Kaoru just floating behind Kouga on her block at the end, it looked so silly.
Instead of some overelaborate fight you could have put in Kouga's farewell from the final episode, and the scenes with the other cast in the end credits there. And maybe have a final good-bye between Leo and Sigma in a peaceful setting. Then Kouga and Kaoru could have a proper last scene together.
Also, did you notice who Sigma was and that he was one of the kids Kouga once trained with?
Weren't they all eaten by that giant Horror?
I hope the third series will be good, but with the cast turnover I'm not sure if I'll like it or not.
I can't really envision Junya Ikeda in the Garo costumes myself.