I would assume you could dispel your own curse at any time, but that could be DM dependent.

Otherwise, until Dispel Magic or Remove Curse are used, it would last forever.

Trying to chase/track a foe that is escaping a fight? Either give them disadvantage on Dexterity or stop them from moving completely on some turns.

Trying to escape someone (or something) that is chasing you? Same as above.

Someone going into an important meeting? Disadvantage on Charisma or Wisdom (lower Insight)

Someone you don't like going anywhere? Give them disadvantage on the roll of your choice.

The biggest thing for casting it at higher levels is the no concentration. Disadvantage on saves, then disintegrate, or banish (Dex or Cha, respectively). Any enemy that has a lower Wisdom than other saves, this makes them easier to deal with.

"At the DM's option, you may choose an alternative curse effect, but it should be no more powerful than those described above." Maybe a small de-buff to an enemy's AC or damage (-2 AC, or  less damage on Strength-based attacks, or vulnerability to a damage type).

Quote from cbowman73 >>

Since this is a touch spell, do you have to roll a melee attack to get it off? It sounds like a spell to use with a familiar or requires some advance setup and be used with the longer duration aspect.

 No, you don’t have to make a roll against the target’s armor class because the spell ignores armor, only needing the slightest brush against target’s person.

Some touch spells (like Inflict Wounds) can be avoided using a DEX save, but in this case you already get a WIS save so that seems redundant.

While I see the pros of this upcasted spell, it doesn't look like much of a good choice most of the time tbh, maybe there's something I don't get, but It's a 3rd level spell, that can be wasted if the target succeed its saving throw, taking one full action during an encounter, and just to pick one of the effects ? On their own, they are really nice effects but going through all of this ? I didn't even mention it's a touch range. I mean, when I look at hex on the other hand, lvl 1, can't miss, disadvantage on rolls with an ability, extra damages, well you can't get rid of the concentration, but can move the spell on a new target and its duration is expanded by upcasting it. Bestow curse looks a bit weak from my point of vue :/ which is unfortunate because I really love the flavour of it. Am I mistaken somewhere ? I see a lot of people finding this spell powerful

Definitely,  I mean 1st level Hex gets you two of those simultaneously.

Remember, Hex is only on the Warlocks spell list, meaning for non-Warlocks it's going to require a dip into Warlock [and possible RP implications] or the use of an Ability Score Improvement to get it with Magic Initiate {or a Bard through Magical Secrets or a.....point being, for most its going to cost a little extra]. Note, Hex is an awesome spell for Warlocks, but it also represents half of there spell slots when used in battle, and as its a spell made for them, its going to play to there strengths and cover there weakness.

Hex does offer no save, can be moved and can be done at a distance {it better be reliable and have lasting power if its going to be one of my two slots]. It also gives part of two effect that Bestow Curse can do [an extra 1d6 necrotic damage to the target whenever you hit it with an attack, along with imposing disadvantage on ability checks of a chosen ability.]. However Bestow Curse also has other options which can be more impactful, such as also imposing disadvantage on saving throws along with ability checks of a chosen ability, or even just skipping the victim's turn entirely. Its flexible, allowing to chose what debuff would be appropriate to the victim/situation, even allowing a player to work with there DM to make up there own curse. Up casting can also get rid of the concentration part of the spell, which makes casting other spells easier, along with opening up additional combos {ie, casting Bane, then casting Curse with the 3rd option for a very simple one.].

Not going to say one is more powerful over another. Hex as a lot of upside not seen on most spells, but is generally lock to and made for one class. Bestow Curse as more limitations {a saving throw and needing to be in touch range], but can also be more game changing with a larger variety of effects should those limitations be overcome.

 EDIT: Just notice Warlocks do get a bit more slots at higher levels. Chalk that up to being somewhat new to the 5e system, and my own shortsightedness of merely going off own experience and not double checking. Most of my opinion I think still hold up, though you may wish to treat it with a grain of salt if applying to the higher level play. {Heck treat all of it with a grain of salt, I'm just some random guy on the internet.}

Bestow Curse (upcast at 5th level) gimping INT + illusions / Phantasmal Force.

Or curse their WIS + Phantasmal Killer.

9th level upcast, for when death isn't remotely good enough.

Quote from Dr_Frederick >>

Quote from cbowman73 >>

Since this is a touch spell, do you have to roll a melee attack to get it off? It sounds like a spell to use with a familiar or requires some advance setup and be used with the longer duration aspect.

 No, you don’t have to make a roll against the target’s armor class because the spell ignores armor, only needing the slightest brush against target’s person.

Some touch spells (like Inflict Wounds) can be avoided using a DEX save, but in this case you already get a WIS save so that seems redundant.

 Inflict Wounds can't be avoided with a dex save, it can only be avoided if the person casting it doesn't meet your armor class on their melee spell attack roll.

With a range of touch, does the spell caster have to make an attack roll in order to touch a hostile creature?

I think this was answered in an earlier post, but "touch" doesn't require a successful attack roll. Touch is just the range of the spell, so you just need to be within 5ft to touch the target, then they need to make a WIS saving throw. A familiar could be used to cast the spell, if you want to keep your caster out of melee range and you have a familiar.

Can you bestow multiple curses in  a single enemy? because if you can that would be amazing to use against a BBEG

If a single person is casting multiple of the spell at low levels, no. Concentration spell. If multiple people cast it at low level, yes. If cast at high level, without the concentration requirement, yes, even by the same person.

I think. That's just my understanding of how it fits into the rules.

Thank you 

Yes.

The bard in my party keeps using it with much success on the following curse : While cursed, the target must make a Wisdom saving throw at the start of each of its turns. If it fails, it wastes its action that turn doing nothing.

Yes there's an initial save, but if failed the enemy just doesn't do much anymore for the rest of the fight. Ok, if save succeded, the bard is supposed to get hit. Still.

What exactly does this mean : If it fails, it wastes its action that turn doing nothing.

Does he keep his move & bonus action and just lose his "standard" action, or does he lose his turn doing nothing ?