If I'm not mistaken, his absolute peak was 2012, 2013 and 2014 up until the knee injury. He was a force of nature, simply supernatural. I think from August - October in 2014 he already had something insane like 20 league goals. But he was incredible from 2006-12 aswell.
After that, Madrid asked him to play differently..closer to goal than before.
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He would've probably been our all-time by now if we signed him even as old as 27 given his goal record since then. He's scored around 200 club goals since turning 30 and Del Piero has the record at 290. But I don't think prime CR7 with the level he displayed at Madrid was attainable. He would have been one of the few players that was truly unsellable. The fact that even at 33 he was still going for 100M+ says a lot (and some Madrid fans even thought that was cheap).