Can't remove ACE from directory

My applications folder has an ACE entry which prevents me from deleting its contents (not even as root, with sip disabled). My problem is, that the command

sudo chmod -N /Applications

tells me, that I have no permission to do this. I couldn't believe it and tried it in both single user and recovery mode, to no avail.

Output of ls -leO:

drwxrwxr-x+ 148 root    admin  uappnd,nodump,opaque  4.9K Jul 31 08:55 Applications/
0: group:everyone deny delete

Is there any other possibility to fix this except from reinstalling the OS?

The proper command to remove the ACE from the folder in SIP-disabled mode is:

sudo chmod -a "everyone deny delete" /Applications

You can also remove (or add) ACL entries by number/index:

sudo chmod -a# 0 /Applications