Originally Posted by Unregistered

Is there any 6* ability that has +150 speed to party aside from Lagurus and Alpinia?

Nope. There are some 5* with +150 though: Creeping Smartweed and Anthurium (both evolved). Dipladenia offers +100 speed while also giving immunity to speed-altering panels, which for some maps more than makes up the 50 point difference.

Looking -far- ahead, another year or so at least, Suziki Grass' 6* Swimsuit form gives +150 speed when evolved.