Big-Lipped Alligator Moment: Where Del becomes the Devil! However, it's actually a sort of hallucinatory version of Beneath the Mask, as Neal is imagining seeing Del as the horrible source of evil he (thinks he) is. It's preceded by a moment where Neal and Del briefly look like skeletons during their Wild Take.
Crowning Moment of Heartwarming: Neal, after mentally piecing together the truth about Del and his wife, returning to the El station to invite Del home with him for Thanksgiving dinner.
Del talking about what his legacy is going to be "when I'm dead and buried," given John Candy's early death. Ditto the final fade-out on his face.
In-universe, Neal's response to Del's above line.
At the very least, the absolute minimum, you have a woman you love that you can grow old with.
In general, a lot of the foreshadowing with Del is meant to invoke this in-universe, to the point of serving as a Rewatch Bonus.
Neal: I've been spending too much time away from home. Del:(casually) I haven't been home for years.
The ending itself is sweet at first glance, with Neal having invited Del home for the holidays and Del getting to be a part of a family again for a moment, until you apply some Fridge Logic and realize that the most likely reason Del smiles wistfully in that final freeze frame is because he's watching his luckier new friend embrace his own wife and the reality of how alone he is just hit home.
Speaking of which, Del's line about how their charred-up rental car is "not much to look at" is the same thing John Candy's character in Cool Runnings says when the Jamaican team reveals their bobsled for the first time.
The Wild Take involving the skeletons is even more hilarious considering what happens to Marv in Home Alone 2.
Jerkass Woobie: Sure, Neal comes off as a bit of a dick at times especially when he snaps at both the rental agent and the taxi driver, but after all he goes through, including nearly dying at least 3-4 different times, could you really blame him for reaching the breaking point?
Values Dissonance: Though generally an inoffensive movie, Del telling the teenage girls that his shower curtain ring earrings make them look like they could pass for older women sounds much too pervy to make it into a contemporary movie.
The Woobie: Del, once it's revealed that Marie has been dead for eight years and he's been homeless ever since.