Filmmakers ranging from Joel Schumacher, Tim Burton to Christopher Nolan, haven't shied away from the portrayal of Batman's fears in the numerous feature films, animated movies, and live-action serials. The classification of Batman's fears may range from phobias to traumas but they are all cyclical in nature, one thing triggers the other and vice-versa.
Batman's scares are very much rooted in his past. Right from his childhood incident of falling down a well and Bats hovering over (Batman Begins), to the murder of Young Wayne's parents, resulting in the fear of Bats and of losing loved ones. Hence, Batman- a symbol of peace as an out-and-out daredevil is a misnomer, because believe it or not, he has his share of scares.
10 BATS
Wayne's phobia of bats is the most apparent. It stems from his childhood incident of falling down a well with bats flying up above him. Because the incident happens at such an impressionable age, it causes extreme fear and becomes impossible to get rid of.
So much so that as a vigilante superhero, Bruce chooses bat as his symbol, admitting to Alfred that they frighten him and it's time the world shared his dread.
9 DEATH
Again, direct admission in Dark Knight Rises is Batman's fear of death. Wayne's fear of dying is an impulse of his spirit that's played on philosophically by the Blind Prisoner. This fear gives his soul the strength to get on and get going with his vigilante mission. Bruce fears to die in Gotham whilst his city burns.
The only time Bruce Wayne is brave is when he is afraid, that is why he listens to the Blind Prisoner and walks without the safety rope, admitting to his fear of death and more importantly of picking up steam from it.
8 LOSS OF A LOVED ONE
Batman's fear of losing a loved one has a deep-seated childhood backstory. This fear has a linkage to his fear of bats. Young Wayne's father, while sensing his sons' trepidation during watching opera performers dressed in black decides to walk his family out. On their way out, young Wayne witnesses his parents' altercation with a mugger, eventually ending in their murder.
The worst of it all: he's left alone to mourn their death in the alleyway and afterward. For Wayne, had he not been frightened in the opera theatre, his parents would have been alive. On his death bed, Bruce's father senses the fear in his eyes and his last words to him are not to be afraid. This would probably explain why Batman chooses to venture into life-threatening situations alone without Robin, Batwoman, and Bat-Family allies.
7 KILLING
Batman never goes for the kill, quite literally. His might solely rests on exploiting the weaknesses and insecurities of his adversaries, at best torturing them into redemption.
Batman has rarely gone blazing guns, with minor exceptions of The Killing Joke, Batman vs Superman: Dawn of Justice. Batman's "no-kill" rule is his devised moral code that acts as his saving grace. Therefore, he's scared to break this rule for his own sanity.
6 FAILURE
The thing about Batman's fears is that all of them are cyclical in nature, one linked to the other. Batman's fear of failure is closely associated with his fear of death. The Dark Knight Rises broaches the subject of failure very closely (Blind Prisoner).
As the Blind guy reminds Batman that not fearing death makes him weak, the latter responds by saying he fears to die and leaving his city behind while there is no one to save it. It is thus this fear of failure that keeps pushing his boundaries and acting on the self promise of "never again" the night his parents died.
5 FEAR GAS
In Batman Begins, when Dr. Crane (Scarecrow) sprays fear toxin, his weapon of choice upon Batman, the latter has some mind-bending hallucinations of bats, his parents' murder before eventually knocking out for two straight days.
Fear Gas is used by scarecrow to induce irrational fears amongst his opponents. Although Batman has been able to attain immunity over it, Scarecrow has used the gas as a pheromone, making it difficult for the Cape Crusader to combat him.
4 DREAMS OF THE PAST
In Dreams in Darkness Batman is an inmate of Arkham Asylum, who's exposed to scarecrow's fear gas. He is hallucinating that if he doesn't do everything in his will, he will see his parents murdered again.
There are countless incidents when flashbacks from the night his parents got murdered haunt, Batman. His childhood is nothing but a horrific memory of it that wrecks him each time he hallucinates or is reminded of it. The death of his parents is single-handedly the defining moment of his life.
3 RELATIONSHIP
In The Lego Batman movie, Alfred in a conversation with Batman says the latter's greatest fear is being a part of the family again. Cue: the night his parents were killed in cold blood, the same night that kicked off Bruce Wayne's career as Batman. Since his beginning is steeped in the tragic death of his family, the Cape Crusader doesn't want to start over with someone again.
And it is not because Batman doesn't want a family or fears commitment but it the logical fear of losing someone that stops him each time. In many other renditions, Batman's fear of relationships has been described as one of the greatest fears if not the greatest.
2 BECOMING THE JOKER
In Batman: Arkham Knight, Batman's mind is warped with Creutzfeldt-Jakob disease, mutated beyond anything on the medical record, slowly turning him into The Joker. Batman, well aware of his talents, abilities, and resources, combined with the traits and personality of Joker would prove destructive for Gotham.
Joker Infection would render Batman an insane force to reckon with, just as eccentric as the criminals he has fought. It is not the physical manifestation that scares Batman the most, but the sole inheritance of personality traits that cause more fear in his mind.
1 HIMSELF
Batman's indomitable fear is that there will come a day when he will no longer be able to fight for the ideals he held so dear. That he would snap beyond repair, no longer protecting the morals such as his "no-kill" code that he stood for all his life.
Batman also fears that from that day onwards, he wouldn't be able to tell the difference between right and wrong causing rampage in the city. In Injustice 2 game, the superhero says that in all his years fighting crime, one thing that he's learned is that every villain is the hero of his own story.