Pete Ross returns after nearly a 4 year absence, and unfortunate for him, it's in the weakest episode of the season.
There are so many minor problems with this episode that all add up. The biggest issue is that it's a lousy plot for an episode. Very cheesy plot and very cheesy powers (seriously, does ingested meteor rock now cause CLOTHES to develop super powers as well?). On top of that you have Kara's amnesia story, which just feels dragged out and repetitive at this point. The relationship between Kara and Jimmy always felt forced, but even more so in this episode. It doesn't make sense that they're apparently so tight when if you actually add up all the scenes they've had together, it's probably less than 10 minutes of screen time all season, and before now, they've never even mentioned spending any real time together outside of the handful of scenes earlier in the season.
Pete himself is a problem with this episode too. It's not completely the actor's fault, but some fault has to lie with the fact that he never gave that much personality to his character. "Hero" in a way is a reminder of how wasted Pete was as a character in the past. It also doesn't help that his absence was close to 4 years. If Pete was going to do a guest spot it should have been incorporated in season 4 or 5, or at least saved for something relevant, and not a cheesy filler episode. The single most annoying this in this episode is the overuse of product placement for Stride gum. All shows have product placement, and even Smallvile's product placement in the past has been worked in effectively (from an advertising POV) and subtly (so as not to feel forced and pull you out of the story). Here it is neither. Still to this day if I ever see Stride gum I laugh and remember how cheesy the placement was in Smallville. "Hero" is probably the worst example of product placement I've ever seen.
However the biggest problem with this episode is still that it's a weak story, and another poor portrayal of a pivotal character in Superman's comic history.