Magikarp has the lowest base steps of 1,530.
Now the highest belong to all of the Pokemon with 680 BST, Celebi, Deoxys, Jirachi, Latias, Regigigas, Cresselia, Darkrai, Shaymin Arceus, Genesect, Thundrus, Landorus, Tornadus all require at least 30,855 steps. But since they cant have eggs you cant hatch eggs of them.
The highest for Pokemon that can actually have eggs would be all of the Pseudo Legendaries, Happiny and evos, Lapras, Munchlax, Snorlax, Unown, Wailmer and evos, Relicanth, Phione, Basculin, Alomomola, Axew and evos with 10455 steps.
Source 1 & Source 2
