Kane and Undertaker destroying each other at WM would've been much better.

They could've had Kane be number 30 at the rumble. Start a feud again. Build the match as the end of Taker. Have crazy shit happen in their match, have a crazy spot where Taker barely beats Kane, and they have some sort of walkout together, having both retire at the same time. Crazy spots would do more damage to Taker, but it would've been the last match. That would be a proper end to Taker's character, and since Kane isn't likely to return, a good end to him too.