First, the entity to summon with a custom UUID pair:

/summon Villager ~ ~1 ~ {UUIDLeast:1l,UUIDMost:1l}

The resulting UUID is: 00000000-0000-0001-0000-000000000001

In 14w08a, you can use the following successfully:

/execute 00000000-0000-0001-0000-000000000001 ~ ~ ~ setblock ~ ~2 ~ minecraft:bedrock

OR

/kill @e[type=Villager]

However, in 14w10b, the command fails with the following error: That entity cannot be found