During the course of Pirates of the Caribbean: Dead Men Tell No Tales, we come to learn that Jack's compass can be "betrayed" and it releases one's greatest fear!
But is Salazar really what Jack fears most?
Consider the following:
Captain Barbossa discovers these ideas when he meets with Shansa, but she never actually confirms that Barbossa's assumption about Salazar is correct, only explaining what the compass can do.
SHANSA: Jack held the compass which points you to the thing you desire most, but betray the compass and it releases your greatest fear.
BARBOSSA: And a pirate's greatest fear be Salazar, is it? How did you get this?
SHANSA: I have my ways.
When one thinks of the films as a whole, the first trilogy sets up a Jack Sparrow redemption arc though what happens to Will and Elizabeth and is reflected through Jack's visit to Davy Jones Locker, which exist as means of punishment (And one may argue that what one fears could be an equivalent to a punishment).
TIA DALMA: Jack Sparrow is taken, body and soul, to a place not of death, but punishment. The worst fate a person can bring upon himself...stretching on forever. That's what awaits at Davy Jones' Locker.
Jack's case seems to be about being stuck with himself, as then he may have to stop and think about some of his choices in life, and not being free to move, as his ship is stuck on land!
JACK SPARROW: Wherever we want to go, we go. That's what a ship is, you know. It's not just a keel and a hull and sails; that's what a ship needs. Not what a ship is. What the Black Pearl really is, is freedom.
In At World's End, Jack then debates if he should become immortal and take over the Flying Dutchmen, but is reluctant because he doesn't want to do the job of ferrying the souls, which would result in him turning into a partial sea creature, like Davy Jones.
Ultimately it is Will that must become the Captain, in order to save his life, but Jack is still partially responsible for putting Will and Elizabeth in a precarious situation, and in which Will can no longer be with Elizabeth as intended.
The next two films start to go further and further in Jack's past, where in On Stranger Tides the ideal replacement for Will turns up on Queen's Anne's Revenge. Philip is a clergy boy who falls in love with a mermaid, and whose film's other antagonist, a scornful ex-love interest of Sparrow named Angelica, is left on a small Island with a voodoo doll that had previous controlled Sparrow.
However, the next film Dead Man Tell No Tales sidesteps the Philip route with the Trident of Poseidon reuniting Will and Elizabeth by another means, continues to go further into Jack's past by showing Morgan, Salazar, and Wicked Wench, but where Jack seems to be out of character, hitting an all time low and being a hallow caricature of himself (not unlike how other versions of himself appeared in Davy Jones locker).
Although it seemed like Jack had redeemed himself with freeing Will, the final post credit scene reveals that Davy Jones may be back, which could make sense if one presumes that The Flying Dutchman "must always have a Captain" mantra is something separate from a curse.
All of this then prompts me to consider that perhaps Salazar was not what Jack feared most, but rather a catalyst to undo various curses and/or restore Davy Jones to helm of the Flying Dutchman, leading to what Jack actually fears most.
So my question is, Is Salazar really the thing that Jack fears most? Do the writers or executive producers actually lay this down as the truth?
Note: International trailer of Dead Man Tell No Tales says, "The Final Adventure BEGINS.", implying the first in series of final films.