The best hand in 2-7 lowball: 7-5-4-3-2, not all one suit.
In 2-7, aces are high and straights count, so neither 7-6-5-4-3 nor A-5-4-3-2 can be the best. Second is 7-6-4-3-2, then 7-6-5-3-2, then 7-6-5-4-2. Fifth is 8-5-4-3-2 (eight perfect). A dealt 5-card hand is a pat 7-high 0.16% of the time.