I'm not sure who the one that submitted the kanji lyrics for this song is, so I'm posting this instead of e-mailing the individual.
I have found a couple of mistakes in the kanji lyrics for: http://www.animelyrics.com/game/kanon/lastregrets.htm
The line "最後まで 笑ってる强さを" (which appears TWICE in the lyrics) uses the Chinese hànzì, 强, on both occasions, and not the the Japanese kanji equivalent, 強. So both occurrence of the above line should be changed to "最後まで 笑ってる強さを".
Also, the line "二人には ありふれた优しさ" has the same problem with the hànzì, 优. So this line should be changed to "二人には ありふれた優しさ"