I'm not going to debate for long, but I would say that there are better late gamers. Look at Thundurus-T. Agility/Thunderbolt/Focus Blast/Hidden Power Ice. Agility + 145 + Modest. Pretty much everything is OHKO'ed. It may lack any priority moves, but nothing is outspeeding Thundurus now except for priority moves - Bullet Punch and Mach Punch which it both resists. Because of the overall move coverage, it requires much less teammate (this was the support I was talking about) support than Lucario.
Gliscor walls you all day if you lack Ice Punch, Jelly walls all day if you lack Crunch. These are the examples, you'll just need to pair it up with another Pokemon such as T-tar. While on the other hand Pokemon like Thundurus can KO or at the worse do some hefty damage to your enemy, its never like its completely walled and you'll just have to switch out (Very, very rare).
I'm not a Thundurus fan, just making a comparison to show the flaws which are in Lucario.
+6 252+ Atk Choice Band Forretress Rapid Spin vs. 4 HP / 0 Def Lucario: 75-88 (26.59 - 31.2%) -- guaranteed 4HKO: Good one
I hope you took my previous post about Rapid Spin as a joke, well despite you mentioning this I still think you took it as a joke.
BOTTOM LINE - Lucario is a great late game sweeper, needs slightly more team support to beat your opponent. Its powerful STAB and priority makes it hard to revenge kill, but as said before like 100 times, you can't punch through everything, unlike most other sweepers/late game sweepers.