Can Genji's shield actually shield all damage when using the right upgrade?
I think it can sort of, i mean there is the upgrade for shield+1 (able to be used twice) and the percentage of damage upgrade which can be upgraded twice as well.
The way genji works is that half his abilities are percentile, and half of them are flat, and you can choose how much of each you want.
By default, his shield blocks a percentage of incoming damage, and you can upgrade it to also block a flat about of total damage, or a flat amount of each incoming attack.
That way if you are up against nukers like clunk or coco, you can block a flat amount of that attack, whereas if you are up against someone that spams little attacks, you can block a flat amount of damage from each.
I found a super effective strategy is yuri+genji, where yuri slows down someone, genji cocoons them easily, and then yuri spams bombs on the cocoon for some scary amounts of damage when they get out.