fedora-userdel: command not found

Have You tried accessing the binary with the full path?

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On CentOS possible default full paths are:

/usr/sbin/fedora-userdel - from package: fedora-usermgmt-core

You may install the required package with command yum install {package}
Error in other languages:
fedora-userdel: bevel nie gevind nie
fedora-userdel: comandă negăsită
fedora-userdel: comando não encontrado
fedora-userdel: commande introuvable
fedora-userdel: command not found
fedora-userdel: käsku ei ole
fedora-userdel: không tìm thấy lệnh
fedora-userdel: komanda nerasta
fedora-userdel: Kommando nicht gefunden.
fedora-userdel: kommandot finns inte
fedora-userdel: komut yok
fedora-userdel: nie znaleziono polecenia
fedora-userdel: níor aimsíodh an t-ordú
fedora-userdel: no se encontró la orden
fedora-userdel: no s'ha trobat l'ordre
fedora-userdel: opdracht niet gevonden
fedora-userdel: parancs nem található
fedora-userdel: perintah tidak ditemukan
fedora-userdel: príkaz nenájdený
fedora-userdel: příkaz nenalezen
fedora-userdel: команда не найдена
fedora-userdel: командата не е открита
fedora-userdel: 命令找不到
fedora-userdel: コマンドが見つかりません