regrettable

As a verb disappoint

is to displease by eg underperforming or disappoint can be (internet slang).

As an adjective regrettable is

of an event, action, or state, allowing or deserving regret.

As adjectives the difference between regrettable and insupportable

is that regrettable is of an event, action, or state, allowing or deserving regret while insupportable is not supportable; incapable of being supported or borne; unendurable; unsupportable; insufferable; intolerable.

As an adjective regrettable

is of an event, action, or state, allowing or deserving regret.

As an interjection alas is

used to express sorrow, regret, compassion or grief.

As a noun alas is

a type of {{l/en|depression}} which occurs in {{l/en|Yakutia}}, formed by the {{l/en|subsidence}} of {{l/en|permafrost}.

As adjectives the difference between disappointed and regrettable

is that disappointed is defeated of expectation or hope; let down while regrettable is of an event, action, or state, allowing or deserving regret.

As a verb disappointed

is (disappoint).

As adjectives the difference between regrettable and infelicitous

is that regrettable is of an event, action, or state, allowing or deserving regret while infelicitous is unhappy or unfortunate.

is likely misspelled.

has no English definition.

As an adjective regrettable

is of an event, action, or state, allowing or deserving regret.

As adjectives the difference between regrettable and unlucky

is that regrettable is of an event, action, or state, allowing or deserving regret while unlucky is unfortunate, marked by misfortune.

As an adverb unfortunately

is happening through bad luck, or because of some unfortunate event.

As an adjective regrettable is

of an event, action, or state, allowing or deserving regret.

As adjectives the difference between regrettable and disappointing

is that regrettable is of an event, action, or state, allowing or deserving regret while disappointing is that disappoints or disappoint.

As a verb disappointing is

present participle of lang=en.

As adjectives the difference between regrettable and unpleasant

is that regrettable is of an event, action, or state, allowing or deserving regret while unpleasant is not pleasant.