Julianna Peña and 4 other UFC champions who never successfully defended their belt

#4. Petr Yan

Petr Yan at the UFC 259 weigh-in

To this day, fight fans regard Petr Yan as the consensus best bantamweight in the world. Arguably the best boxer in the UFC, 'No Mercy' captured championship gold by defeating José Aldo for the then vacant bantamweight championship at UFC 251.

At the time, Yan was heavily criticized by current bantamweight champion and divisional rival Aljamain Sterling for what 'The Funkmaster' described as an easy path to the title. Before facing José Aldo, the Russian phenom had faced the 40-year-old Urijah Faber.

Yan's matchup before facing Faber was against Jimmie Rivera: a quality win. Before that, however, the previous bout was against John Dodson, a former flyweight. Thus, it was not difficult to understand Sterling's gripe with Yan's path to the title. Nevertheless, 'No Mercy' successfully captured the title against José Aldo, leading to a hotly anticipated bout with Sterling at UFC 259.

When the two finally clashed, Yan seemed a class above Sterling, dropping him with punches and securing multiple takedowns in a highly convincing performance until the Russian, for some inexplicable reason, slammed an illegal knee into Sterling's head while his foe was grounded on his knees.

With Sterling unable to continue the bout due to the force of the blow, the referee was forced to declare the contest a disqualification, not only causing Petr Yan to lose his championship without managing a single successful title defense, but also causing him to become the first UFC champion to lose a title via disqualification.

---

#3. Eddie Alvarez

Eddie Alvarez at the UFC 205 weigh-in

Also known as 'The Underground King', Eddie Alvarez is one of the few mixed martial artists to have won a world title in both the UFC and Bellator. Halfway through 2016, Alvarez was riding a 2-fight win streak that earned him a title fight with lightweight champion Rafael dos Anjos.

At the time, RDA seemed unbeatable, having captured the title from Anthony Pettis in dominant fashion before brutalizing Donald Cerrone within a round to net his first title-defense. On a five-fight win streak that included former lightweight champion Benson Henderson, RDA was thought by many to be set for a long run at the top of the division.

However, when Eddie Alvarez challenged him for lightweight supremacy at UFC Fight Night 90, 'The Underground King' shocked the world. After 2 minutes of a fairly even affair, Alvarez rocked the Brazilian with a long right hook. RDA never recovered and Alvarez battered him against the fence until Herb Dean mercifully stepped in to end the bout.

Alvarez's next bout was his most memorable. 'The Underground King' locked horns with Conor McGregor in the latter's attempt at becoming a two-division champion in the UFC. Alas, at UFC 205, Eddie Alvarez was on the losing end of one of the most dominant championship performances in MMA history.

McGregor defended every takedown attempt while outstriking his foe, dropping him multiple times before earning the second round TKO win in effortless, karmic fashion after Alvarez had described the Irishman as the easiest fight in the division.