That's my point exactly, he has a lot of ending lag for some of his moves, it's one of the reasons why he's a bad characters. Don't get me wrong, really good Lucas mainers can kick a lot of ass ofcourse.
His U-smash is obviously one of the strongest in the game, but Ivysaur's is stronger, has less start up and cool down lag too.. Lucas got the short straw compared to Ivysaur. -.-' Lucas has a ton more cool down lag than Ivysaur, that's for sure.
Lucas is very different from other bad characters. If you can predict well with his lengthy moves, he's very scary. D-smash can hit someone directly behind you, just barely tap anyone who rolled away, or smash side step dodges. Large KO powers too. F-smash is just a plain good move, and his U-smash is possibly his best AND worst move, as if you land it, odds are you just got a kill if it's fresh.
PK Thunder 2 also does huge damage and good knockback ofcourse, and has great range. If you predict it right, you can use this as a great suprise attack. And ofcourse, that's only a few of his options. He also has a few glitches to use to his advantage. If his recovery wasn't so gimpable(like Link's, but his is much better), he'd be a great character.