Probably always Late Rival 2 with 12/x/x or less

Early Rival 2:

When to get X Attack:
27 or less attack at Lv16 (all/12/0 or less) OR 33 attack (x/x/26 or more)

With 23-24 Attack: Leer+Leer+Leer+QA+X Attack+QA+Tackle+QA
With 25-27 Attack: Leer+Leer+X Attack+QA+QA+Tackle+QA
With 28-32 Attack: Leer+Leer+Leer+QA+QA+Tackle+QA
With 33 Attack: Leer+X Attack+QA+QA+Tackle+QA

Late Rival 2:

When to get X Attack:
29-33 Attack at Lv19 (16+/0-20/0-4)

28 or less attack: Leer+Leer+Leer+QA+QA+Tackle+QA
29-32 attack: Leer+X Attack+QA+QA+Tackle+QA
33 attack: Leer+QA+X Attack+QA+Tackle+QA
34-37 attack: Leer+Leer+QA+QA+Tackle+QA
38 attack: Leer+QA+Leer+QA+Tackle+QA