Grey's Anatomy didn't become the longest-running medical drama of all time without providing a few shocks along the way. Even in its 15th season, Grey's continues to be an undefeatable monster in the ratings. It's ABC's highest-rated drama and as rarely been beat in its many years, dominating the network.

Related: The 5 Best (& 5 Worst) Episodes Of Grey's Anatomy Season 13

Although it doesn't claim the same critical attention or award nominations as it did in its early days, Grey's Anatomy is still more than capable of delivering an emotional gut-punch or nail-biting cliffhanger. Before the show returns this fall for its 16th season, we're ranking the series' best (and worst) cliffhangers out of its entire run.

Worst: Jackson Vanishes In The Fog

This cliffhanger occurs in the most recent finale of Grey's Anatomy. At the end of the final hour of season 15, Maggie and Jackson are attempting to rush back to the hospital to aid their patient when Jackson gets out of the car to check what's causing all the traffic in the dense fog. He doesn't come back. Maggie gets out to shout for him but he doesn't seem to hear her... and then the episode ends.

The issue with this cliffhanger is there is no sense of suspense. News broke of Jesse Williams renewing his contract within days, so we know Jackson isn't dead. That doesn't mean he couldn't be injured, but it's a fairly weak cliffhanger based on others we've seen on the show. Andrew's cliffhanger behind bars is a far more interesting season 15 cliffhanger, no question.

Best: Arizona And Callie's Car Crash

Callie Torres and Arizona Robbins standing together in Meredith's living room in Grey's Anatomy

Callie and Arizona are driving when Arizona suddenly springs a proposal on her. Before Callie gets the chance to answer, they end up in a terrible car crash. It's an intense scene and made even more so by the fact we don't get Callie's answer and their lives could be hanging in the balance.

The cliffhanger in question occurs during the season seven episode "This Is How We Do It." Of course, all of this is made scarier by the fact Callie was pregnant at the time and no one knew if the baby would survive, nonetheless Callie, who bore the brunt of the crash.

Worst: Teddy Is Pregnant With Owen's Baby

Fatigue over the constant back-and-forth between Teddy, Owen, and Amelia had reached a critical point already by the end of season 14. When it was revealed that Teddy was coming back to be a legitimate series regular and was pregnant with Owen's baby, people weren't as shocked as they were annoyed.

Related: Grey's Anatomy: The 10 Hardest Hitting Break-Ups

Grey's Anatomy has had an Owen Hunt problem for years. He constantly sabotages relationships and can't seem to learn from his mistakes. By the end of season 15, it appears he and Teddy are finally on the same page but we've seen this relationship play out numerous times already. This cliffhanger came too little too late.

Best: The Plane Crash

Meredith sitting among the wreckage of the plane crash on Grey's Anatomy

Grey's Anatomy featured a traumatic plane crash at the end of its eighth season, one that ultimately robbed fans of two favorite characters: Lexi Grey and Mark Sloan. Over the years, the crash has been parodied and made fun of as one of the more ludicrous twists and cliffhangers on the medical drama's long history but to this day it has hardly been rivaled by any other drama series.

If it were another show, the writing might not have been up to snuff to execute this properly. Grey's has always had an excellent team of writers and they helped make this one of the best and most memorable cliffhangers of the series.

Worst: Alex Beats Up DeLuca

This was not one of Alex Karev's finer moments. He comes home and finds DeLuca with Jo and instead of trying to understand what the predicament was, Alex jumps to the worst possible conclusion and beats up Andrew. It wasn't a great moment for the character who has grown so much since the first season of the show.

Fans were disappointed in this turn in Alex's storyline and then it became prolonged as the possibility of Alex going to jail became increasingly likely. The hatred that once brewed between these two has hardly been mentioned since which is especially odd since Alex's best friend is now dating him. It appears that the writers might want to forget this hiccup, too.

Best: The Hospital Shooting

The end of season six may be the most shocking and unexpected season finale out of all 15 seasons of Grey's Anatomy. Gary Clark returns to the hospital after his wife had been taken off life support to seek revenge on the doctors and nurses. He begins to shoot at any doctor that he comes into contact with.

Related: 5 Of The Best TV Pilots (& 5 Of The Worst)

The finale was another two-parter and at the end of the first hour, Derek has been shot in the chest and left in near-fatal condition on the hospital floor. Cristina and Meredith are hysterical as they hover above him before jumping into action and saving his life.

Worst: Owen's Sister Is Actually Alive

And the award for the least shocking cliffhanger of all time goes to... this moment in the penultimate episode of the show's 13th season. Everyone predicted that Megan Hunt was secretly alive. Critics had been calling it since the beginning of the season. Fans had pieced together clues long ago.

RELATED: Grey’s Anatomy: 10 Times Meredith Was Actually A Jerk

Megan arriving back on the scene shocked virtually no one. Perhaps the circumstances were different than what anyone anticipated but the point is, as far as cliffhangers go, this one was incredibly weak. It also created a boring storyline with Megan, Riggs, and Meredith, despite the fact no one was ever all that invested in Riggs to begin with.

Best: Denny's Heart Won't Start

Izzie in formal dress cuddles up to Denny in hospital bed in Grey's Anatomy

The two-part season finale of season two is another one of the most iconic cliffhangers of all time. Grey's Anatomy delivered a heart-stopping ending (bad joke, sorry) to one of their most critically and fan-beloved seasons. Between Burke's hand surgery and Denny Duquette, it's hard to know where to begin. The sad love story between Izzie and Denny has to come out on top.

Related: Grey's Anatomy: Most Heartbreaking Deaths, Ranked

From cutting the LVAD wire to trying desperately to get his heart to stop, the first part of this two-hour finale left every fan on the edge of their seat. Erica Hahn tried her best to get Denny's new heart to beat and it wouldn't! Ultimately, it does but then Denny dies anyways. Grey's truly knew how to pull your heartstrings even from the very beginning.

Worst: Jackson Confesses That He Loves April

Regardless of your feelings on the now infamous Japril pairing, most would agree that this scene was supremely tacky. There's nothing wrong with the eventual pairing of Jackson and April but this cliffhanger in the twelfth episode of season ten didn't leave either of them in a good light.

What person in their right mind would stand up in the middle of a wedding ceremony to confess their love for the bride? Even worse, Jackson did it while sitting next to his then-girlfriend, Stephanie. It was clear Jackson and April had feelings for each other but he just should have told her before the ceremony, at the very least, rather than in the middle of it!

Best: Addison Montgomery Shows Up

Derek and Meredith talk to Addison on Grey's Anatomy

Is this cliffhanger the most dramatic out of all 15 seasons of Grey's Anatomy? No, it doesn't contain any death scares or medical emergencies, but at the time, it was a massive shock for fans of the show... particularly those who were rooting for Meredith and Derek to get together.

Even now, Addison's entrance and the revelation that Derek was married, is considered iconic. It was the perfect way to wrap up the show's first season. Its legacy lives on as one of the most shocking moments of Grey's, even if it was outshined by bombs, plane crashes, and shootings since then. This was the cliffhanger heard round the world and helped make the second season of the show one of the most-watched ever.

Next: Grey's Anatomy: 10 Episodes We Still Watch Over and Over