Skewer sphere (5e Optimized Character Build)
From D&D Wiki
This build is focused on trying to make the Battlerager spiked armor as large as possible, this is obviously meant as a theoretical build to make a stupid character.
The battlerager subclass is limited to dwarves, but with DM permission you can play as a different race, so either play as a duerger because they can cast enlarge on themeselves, or as a bugbear which increases the reach of all melee attacks you make on your turn by 5ft.
1-3: Go battlerager so we can actually use the spikes.
4-6: Go primeval guardian, this gives you a transformation which, among other things, increases the reach of ALL melee attacks by 5ft.
7-20: Go giant soul sorcerer, this also gives a transformation which increases reach of ALL melee attacks by 5ft, choose hill giant as it gives enlarge/reduce
The highest reach available is 20ft, while the highest length is 40ft (due to enlarge technically doubling its length).
So you have multiple, 40ft long spikes extending out from you.