Well, if we take the Bible as true, blasphemy and suicide are two things you can't repent from.
Also - when do we repent? Do we get the chance to repent once we're dead, or do we have to do it before we die?
blasphemy is unrepentable, because if you a blasphemer, and actively argue against god, odds are you wont want his sympathies, hence you cant repent, blasphemy and swearing are two different things, contrary to popular belief
and suicide is unrepentable because (and this will answer your other question), to repent, the steps sort of go somethinglike: you do something, realise its bad, feel genuinely sorry for it, and ask for forgiveness, and understand why it was bad and how, if its a bad habit you try to curb it as best you can and pray for strength to help you, and if its a one off thing you dont let it happen again.
suicide is unrepentable because a) youre sort of throwing away the gift of life youve been given and its really disrespectful, like if you blow up somebodies car, you are probably the worlds biggest dog and just did a really fucked up thing yeah, but eventually you could pay it back, and you might not even fully comprehend the feelings of others if youre young and dumb, but if someone else saves up for ages, and buys you a car, and then you say "lol fuck you" and blow it up, its on like an entirely different level of cold heartedness if you get what i mean?
but that first point is arguable, the main reason is b) in order to be forgiven, you must repent whilst alive, and realise the badness of your actions, so lets put in a big example here and say murder, the steps go something like this
get really angry -> kill somebody -> be really sad and think oh fuck oh fuck -> realise what youve done, probably cry about it, say how sorry you are, show remorse -> pray for forgiveness, talk to a priest and let him know how bad you feel, -> reform -> the sin has been forgiven provided you are being sincere about it all -> youve grown as a person
whereas if you commit suicide its more like
kill somebody -> its you -> go straight to after life-> no chance to repent
see, there was no time to repent in there, everyone would repent in the afterlife because they would see the folly of their actions in their human life, therefor everyone would be forgiven, and that wouldnt work because then people who are really mean would just want to escape so they would repent too, so it is up to you to ask for forgiveness now whilst alive to show that youre sincere
sorry, i have nothing to add to the morality argument, i was just answering brendens question