Turn 1: Sacred Fountain, pay life, Akroan Crusader
Turn 2: Plains, Ordeal of Heliod, Attack for 3
Turn 3: Plains, Fabled Hero, Attack for 4
Turn 4: Coordinated Assault on heroics, Attack with all (Akroan Crusader 4/4, Fabled Hero 4/3 with double strike and 2 tokens 1/1) for 14 and sacrifice Ordeal and gain 10 life
Total: 21 Damage
Turn 1: Sacred Fountain, pay life, Akroan Crusader
Turn 2: Plains, Precinct Captain, Attack for 1
Turn 3: Plains, Ordeal of Heliod on Akroan and Coordinated Assault on Akroan and Captain, Attack with all (Akroan Crusader 3/2, Precinct Captain 3/2 and 2 tokens 1/1 each) for 8 and put 1 more token
Turn 4: Spear of Heliod, your creatures will get +1/+1 so Akroan Crusader 4/4, Precinct Captain 3/3, and 3 tokens 2/2 each causing 13 damage and put 1 more token
Total: 22 Damage
Turn 1: Sacred Fountain, pay life, Legion Loyalist, Attack for 1
Turn 2: Plains, Phalanx Leader, Attack for 1
Turn 3: Mountain, Anax and Cymede, Attack for 2
Turn 4: Martial Glory and Coordinated Assault on Heroics and attack with all (Anax and Cymede 11/6, Phalanx Leader 6/8 and Legion Loyalist 5/5) for 22
Total: 26 Damage
Turn 1: Mountain, Akroan Crusader
Turn 2: Mountain, Legion Loyalist, Coordinated Assault, Token with haste, Attack for 5
Turn 3: Plains, Anax and Cymede, Attack for 3
Turn 4: Plains, Martial Glory on Heroics and Ordeal of Heliod on Anax (3/2 +3/+0 +1/+1(Ordeal) +2/+2(Heroic) = 9/5), and Attack with all (Legion Loyalist 3/3, Akroan Crusader 3/6 and 2 tokens 3/3 each) for 21
Total: 29 Damage
Turn 1: Sacred Fountain, pay life, Legion Loyalist, Attack for 1
Turn 2: Plains, Phalanx Leader, Attack for 1
Turn 3: Plains, Fabled Hero, Attack for 2
Turn 4: Mountain, Martial Glory and Coordinated Assault on Heroics, Attack with all (Phalanx Leader 4/6, Fabled Hero 10/6 with Double Strike and Legion Loyalist 3/3) for 27
Total: 31 Damage
This in case of perfect games but there so many possibilities to populate the field with your creatures and tokens and make than stronger enough to cause high amount of damage