pt-kill: command not found

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 Debian possible default full paths are:

/usr/bin/pt-kill - from package: percona-toolkit

You may install the required package with command apt-get install {package}

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