When considering the risks of backpacking the PCT, I think its misleading to only look at thru hiker incidents on the PCT. I think the better data for evaluating risk is to look at backpacker incident data in the cascade range in Washington State. Unfortunately filtering the data in that way is very difficult, so I have provided some state-wide information and some information specific to the PCT.
The number one cause of death or injury on the PCT, by a lot, is falling off the trail. The PCT is a crest trail with many miles of dramatic drop-offs.
The last death on the WA PCT was in 2018 when a woman fell off the trail immediately south of Kendall Katwalk.
The number two cause of death is drowning during a creek crossing. Use extreme caution in all creek crossings.
One hiker was found drowned in 2" of water (possibly a seizure or a fall). For tips on crossing safely see the page about the four most risky stream crossings in WA.
Aside from those top two causes of injury or death, these other causes are much more rare and are also more weather dependent.
++++ No PCT hiker in WA has ever reported an attack by a wild animal ++++
The animal most likely to bite you while you are hiking is another hikers dog.
For context, you are more likely to be struck by lightning while hiking than you are to be attacked by a wild animal. In the last 30 years, four people have been killed by lightning in WA (Washington has the least human lightning strikes of any state in the US.)
Cougars (aka mountain lions)Cougar attacks on humans are extremely rare. The WDFW estimates WA has 2,000 cougars. In the last 100 years there have been 20 human injuries by cougars and two deaths in WA, one in 1924 and one in 2018. Many victims have been children. None have been on the PCT.
Note, The Issaquah Zoo has a number of native cougars. If you have not seen one up close, I recommend it. These animals are very much lions.
BearsGrizzly bears are much more likely to attack a human than a black bear. The very few grizzly bears in WA are close to the Canadian border. Most bears in WA are black bears. The WDFW estimates there are 25K to 30K black bears in WA. That should give you some idea of how often there must be non-eventful encounters between hikers and bears. There have only been five bear attacks on humans in WA in the last 100 years, only one fatal. Two were children, one was a hunter injured by a bear she shot, one was a biker with an unleashed dog. This is consistent with continental black bear attack statistics: most often a shot bear attacking a hunter, a bear chasing a dog back to its owner, or a child. Bear attacks are trending up overall in N. America, but are still extremely rare.
WolvesNo wild wolf has attacked a human in the continental US in the past 100 years. Sadly they have been so mercilessly hunted there are less than 200 in the entire state. You are unlikely to ever come near one.
CoyotesCoyotes are abundant. No wild coyote has attacked a human, but they are happy to go after your dog or make a snack of your cat. I love seeing coyotes, I think they are beautiful.
Murder HornetsMore an interesting development than a PCT risk: Last year two murder hornet nests were found and destroyed in Washington just south of the Canadian border, west of North Cascades National Park.
Fun fact #1: Men are 80% more likely to be attacked by bees, wasps, or hornets. I interpret this to mean the men are 80% more likely to piss off animals than women.
Fun fact #2: Men are 86% more likely to be struck by lightning. I interpret this to mean the men are 86% less likely to avoid lightning than women.