Correct spelling, explanation: successful is an adjective and it consists of two elements: the root (success) and the suffix (-ful). You can’t change the spelling of any of these parts. The noun success must be spelled with the double -c and the double -s and the ending -ful need to be spelled with just one -l. Full with two -l letters is an actual word. Successful is the only correct version and sucessfull is not correct.

Definition of successful:
adjective, achieving the results wanted or hoped for
If you are successful, you can expect a promotion.
She seemed destined for a successful career.

Collocations with successful:
Some most commonly used collocations include: extremely successful, incredibly successful, and commercially successful.
The event was extremely successful and positively received by the industry.
The band was incredibly successful in the eighties.
All the shows were commercially successful.

Incorrect spelling, explanation: you can’t spell the word successful as sucessfull, because that would be a mistake. This adjective may seem complicated to some English users due to the accumulation of double consonants. Remember that it’s a derivative of the noun success – and this noun must be spelled with the double -c letter and the double -s letter. It means that sucessfull can’t be correct.

Incorrect spelling

Incorrect spelling

Incorrect spelling

Incorrect spelling

Incorrect spelling