Wanna see something depressing?
Loot boxes are garbage - #11 by FatBluDragon-2951
On this Thread, I calculated how many lootboxes are needed to get a specific chance of getting at least one legendary lootbox.
If you want a chance of 98% to get at least one legendary lootbox, you have to open at least 51 of them. For a chance of 90%, you need to open at least 30 and, for a chance of 50%, you need to open at least 9.
The higher your desired chance, the more lootboxes you need to open.