1) Active 2) Authoritative 3) Best 4) Big 5) Cogent 6) Determining 7) Effective 8) Formative 9) Important 10) Large 11) Leading 12) Persuasive 13) Potent 14) Powerful 15) Seminal Found on https://www.crosswordclues.com/clue/influential
[Adjective] Having the power to affect people or events. Example: In the 1980s Mrs Thatcher was an influential politician.
Found on http://www.bbc.co.uk/skillswise/glossary/
In`flu·en'tial (ĭn`flu*ĕn'sh a l) adjective [ See Influence .] Exerting or possessing influence or power; potent; efficacious; effective; strong; having authority or ascendency; as, an influential man, station, argument, etc. « A very influential Gascon p... Found on http://www.encyclo.co.uk/webster/I/55
adjective having or exercising influence or power; `an influential newspaper`; `influential leadership for peace` Found on https://www.encyclo.co.uk/local/20974