Which is the only animal to eat bees?

There are quite a few animals that eat bees.

Wasps will kill and eat them on occasion.

Bee eaters, which are various species of birds that live in Africa and Eurasia, often hunt and kill bees. Most are in the species Meriops.

https://www.beautyofbirds.com/beeeaters.html

Here is an article on the Bee eaters (birds).

http://montereybay.com/creagrus/bee-eaters.html

The species of birds is called Meropidae.

https://en.wikipedia.org/wiki/Meropidae

Also yellow spotted lizards according to this page:

http://wiki.answers.com/Q/What_insect_or_animal_will_eat_bees_and_yellow_jackets_and_hornets

Frogs and toads are general insect feeders and they may
include an occasional bee in their diet.

https://canr.udel.edu/maarec/wp-content/uploads/sites/18/2010/03/Pests_of_Honey_Bees_PM.pdf

There was a book produced by New Scientist magazine a few years ago with the title "Does anything eat wasps?" I would guess that most creatures that eat wasps would eat bees too.

Bees eat bees:

Bees can be ruthless relatives. Bumblebee queens eat their offspring's eggs, and honeybee workers make meals of their siblings' eggs.

http://www.livescience.com/animals/061211_mm_bee_eggs.html

Dogs like to eat bees and some are allergic to the sting:

http://life.familyeducation.com/dogs/first-aid/45654.html

My dogs ate bees...I was allergic to the vet bills.

Spiders will if they've got a strong enough web. When bee eaters nested in County Durham a few years ago, I remember a hive of bees was brought in to make sure they got enough food.