Checking a +1/+1 counter requirement
A creature with two +1/+1 counters has a +1/+1 counter, so Abzan Battle Priest's static ability will grant that creature lifelink.

Note that being granted +1/+1 and having a +1/+1 counter are very different. If you control Dauntless River Marshal, Abzan Battle Priest and an Island, the Marshal won't be granted Lifelink.