Yes MrLavender, you are right.
I did a second user and it can run gitk without segmentation fault.
Is it a way to see what is wrong with my account?
Like making a diff between of some directories of the two accounts or see what settings files tk uses?
You have core dumps. But sadly you’re on stable branch, so they won’t be of any help probably. 
I don’t use Xfce so have no clue where to start looking. Hopefully someone who does can take it from here.
man gitk
says that the configuration file is supposed to be in
$HOME/.gitk
I don’t have that - because I just tested but do not use the program, so it is not configured.
There is also
$HOME/.config/git
but that is also empty here
Perhaps try using Bash instead of zsh.
Did you change the shell to zsh system wide?
I know nothing else.