Lesotho -- it's border "forms a complete loop"? Wouldn't most countries that aren't split into multiple islands be like this? Presumably you meant that it is landlocked, so maybe "whose land border forms a complete loop" would be more accurate?
Well, yes, but there is only one island nation in the world that has only one island (Nauru) and it has a considerably shorter border, so that is not a possible answer (neither does it start with L).