how would you stat a Giant archer as a PC in 5e?

>>54173993
Goliath race and ranged Fighter/various other classes capable of using bows is the best you're gonna get with 5e DnD.

>>54173993
This >>54174152

If you're starting at level 5 or higher, i would also say to have him use the DMG optional rule that has you make a single attack instead of multiples and compound the damage, so that rather than two shots for 1d10+stat it's one for 2d10 plus double stat.

That helps get across the draw weight he's working with. If you want to take it a step further give him a 'giant longbow' statted up as a magic item that does 2d6 damage and can substitute Strength for Dex.

It'd be a lot of damage in a single shot, but it wouldnt be too overwhelming.