LED/DME sometimes need specialist agents to check the visa due to the Cyrillic used in the stamp (so as to check it is still valid date wise etc) - same for any country not using Latin script. Hence it is best to arrive a bit earlier, but if you turn up one hour before departure then that is still OK, after all connecting passengers could be trying to get through Flight Connections downstairs until 35 minutes before departure.

If you don't have a visa for Kiev then just give yourself a few minutes if HBO, to pass by the Visa Check desks, as you would for the USA, Canada, Australia. It's not so much that there is a visa check (difficult if you don't have a visa!) but it's to clear down Ready to Fly. If Emerald then you don't even need to do that frankly, the First Wing will just scan the passport in just before the boarding pass gate. If checking in luggage again you don't need to allow extra time since the 45 minute cut off carries that through. All it is to tick a box for Ready to Fly purposes which takes a second or two.