1. What does it mean?
사기캐 shortens 사기 캐릭터. It describes a character whose strengths seem so great that playing against them feels unfair. Figuratively, it can praise a person with an impressive combination of talents.
Also written or said as sagikae
2. The nuance
사기 here is exaggeration, not an accusation of fraud or cheating. A player's opinion about a character may depend on the matchup, patch, and skill level.
3. Examples
“회복도 공격도 강해서 사기캐처럼 느껴져.”
The healing and attacks are both so strong that the character feels overpowered.
“노래에 운동까지 잘하니 진짜 사기캐네.”
Being good at singing and sports too is an unfair amount of talent.
Sources
References support the meaning and usage. Example sentences are written for NoCapWiki.