Redemption

Savage Worlds suggests that Miracle casters (ie, Clerics, Paladins, other holy types) have a rough understanding of their religion's taboos, and take a -2 penalty to cast spells for a week when they "sin" and break a minor taboos. If you don't play SW, that's a significant penalty. More serious violations cause a complete loss of their Divine power until the character undertakes a quest for atonement.
Most forms of D&D have similar mechanics, though the Atonement spell often wussifies it.
These quests are an awesome opportunity for DMs to railroad their party into doing what they're told for a few sessions. A few sessions means that the players get to spend time telling the cleric "this is your fault," when things go bad. In general, it should be an adventure for everyone. The cleric should be the hook, but the heroics should be shared as normal. Obviously, it should be fun (for the players) and challenging, so there's no way to be specific about what they face. Here are the basic plots:
1. Rescue the Stolen Relic from the bad guys.
2. Find the Lost Relic before the bad guys do. (same thing, only whoever has it doesn't know what it is)
3. Cleanse the Desecrated Holy Place.
4. Pilgrimage to The Holy Place. (Only works if getting there is dangerous)
5. Follow the Leader (a pilgrimage retracing the steps of the God/Prophet/Saint)
6. Banish the Enemy, defeating a powerful supernatural evil (a Demon, for example)
All of these lend themselves to pretty standard adventures, so that's not a problem, and most of them can actually be incorporated into a prefab adventure with minimal effort. Change the generic +2 Mace in the refuse pile in the room to the side right before the BBEG's chamber into the Scepter of Ramalamadingdong, the most holy King of That Place, who drove the weasels out of Finland. Make it shine with holy light and you have a Find the Lost Relic. Put it in the BBEG's hand, and it's a Rescue the Lost Relic. Make the ruined city be the birthplace of the God, and have the players drive out the infidel to make it safe for the faithful.
The Religion in my game world is pretty monolithic, but there are sects. For my own edification, I am going to present the most militant (i.e. PC-friendly) sect - The Awakened Flame.
The symbol is a torch.
The Priests are called Guardians.
The holy hour is sunset, holy day is the winter solstice. The Enemy are nightmares (aka demons, devils, angels etc) and those who traffic with them (conjurers, necromancers, etc. magic users) They light torches at sunset, and massive bonfires at the solstice. They are all about fighting the darkness, literal and figurative.
The minor sins are: extinguishing flames at night, sleeping at night without a Guardian on watch, fleeing from a powerful (relative to the character) Enemy, allowing the weak to be threatened by the Enemy, sparing an Enemy, failure to observe the holy hour.
Major sins: allying with the Enemy, allowing the Enemy to desecrate a holy place, failure to observe the holy day, failure to protect the weak.
Redemptive quests will often be of the Banish the Enemy sort, though there are a number of relics from the Awakening Wars, when the Guardians first appeared and held off demonic hordes for critical days while the First Awakened worked the spell that separated reality from the dreamworld of magic and evil.
In Savage Worlds, a priest who takes the AB: Miracles (Guardian) Edge automatically gets the Smite power, in addition to the two they normally choose. This power (and any other Guardian power that is appropriate) has fire trappings, meaning that anyone hit rolls 1d6. On a 6, they catch fire.