Kendra Wilkinson RIPS Crystal Harris ... 'I Wanted to Kill Her'

Hugh Hefner's new bride Crystal Harris is lucky she's alive ... because Hef's old GF Kendra Wilkinson says she wanted to KILL Crystal for previously dumping the Playboy mogul.

Kendra was on the Big J Radio Show in Montana this morning when the host asked about Hef and Crystal reuniting in matrimony ... and KW blew up, saying, "I got pissed off when she hurt him."

Kendra continued, "That pissed everybody off that she would just leave him and dump him, use him and abuse him." Then added, "I wanted to kill her."

You'll recall, 26-year-old Crystal abruptly ended her first engagement to 86-year-old Hef in 2011 just days before their wedding. The couple patched things up last year and eventually married on New Year's Eve.

But don't worry, Kendra's not holding a grudge -- saying she only wants to see Hef happy.