One of my favorite ways of making resurrection (and the like) risky was how they handled that spell in 13th Age, with various possible repercussions. I keep meaning to transfer that into 5E, and keep forgetting when the time comes.
I forgot where I got this (interwebs, and I made a few modifications myself...), but I use the following:
"The standard Dungeons & Dragons rules for returning from the dead via spells like Revivify, Raise Dead, Resurrection, and True Resurrection do not impose enough of a penalty. In order to make death a bit more risky, and have some lasting consequences, the following rules will be implemented.
Afterlife Escalation
Each time a creature is brought back to life via magic, a piece of their soul remains in the afterlife. They may only return from death a number of times equal to their [Constitution modifier + 1], before their soul is permanently anchored in the afterlife. An additional death is the absolute end for that creature, after which they may not be brought back to life by any means short of direct divine intervention.
Fragile Soul
Outside of the body, the soul is somewhat fragile. The process of bringing a person back to life is hard on it, and there's a chance a returning soul could be lost or destroyed in the attempt. A caster attempting to revive the dead must make a spellcasting check with a DC from the appropriate table below.
- On a success, the victim must make a System Shock roll [Constitution save, DC equivalent to the spellcaster check], or lose experience points equal to one level.
- On a failure, the victim makes the System Shock roll mentioned above at Disadvantage, and the caster must roll percentile on the same table to ascertain the fate of the soul.
Revivify: DC 15+1/round
01-64 spell works as normal
65-88 soul not returned to the body; spell slot and materials expended
89-96 soul not returned to the body; it is lost in the void instead
97-00 soul returned to body, but the spirit of an outsider (such as a demon, devil, angel, etc) crosses over as well. Will contest [d20+Int,Wis,Cha mods] to see who controls body