God: just AND merciful

Some people think of God as an unbelievably lenient sky fairy whose one wish is to gratify His believers. You only have to follow His commands when they're easy. If they're not, God doesn't care. The Bible is open for interpretation anyway, so just be generally good and you'll get into Heaven. But this is not the God we serve. See, we are saved by faith, but as James warns us in his epistle, true faith is accompanied by obedience. If your faith is not accompanied by works, it is a dead faith, so can it really save you? Even the truly faithful can receive God's judgements here on the Earth, for the word tells us "For whom the Lord loveth he chasteneth, and scourgeth every son whom he receiveth." (Hebrews 12:6). If you aren't even remotely scared that God might ever be angry with you, your "god" is you.

But just because God must punish all sin, that doesn't mean you must take that punishment yourself. Ezekiel 18:32 and 33:11 both tell us that God takes no pleasure in death, but would prefer we repent and live. 2 Peter 3:9 further tells us that God is not willing that any should perish.

The character of God, therefore, is neither indifferent, nor merciless. Rather, God is a harmonious mixture of just and merciful. If your god doesn't care about sin, he isn't real. If your god hates you enough that you must work for salvation, he also isn't real. The real God hates sin, to the extent where He cannot look at it (Habakkuk 1:13), but He loves sinners so much that it is Christ who paid the price for our redemption (Romans 5:8). But only if you repent (Matthew 4:17).