For Ethiopia (Abyssinia), Italy tried to not leave them alone, and failed in 1896, and then managed to successfully not leave them alone, if only for a brief time, in 1935. In the interim, while Ethiopia may have managed to avoid being colonized by European powers in the period, they weren't left alone. This older answer of mine should be of interest, looking at one aspect of this, specifically focusing on the international arms trade, and European attempts to isolate and weaken Ethiopia.