Sufficive is not a word. People use this non-word in the phrase "sufficive to say" when they've actually misheard the correct phrase, which is "suffice it to say."
I have several online dictionary sources I use. I checked all of them and others as well. Sorry, couldn't find it with either spelling. THEE dictionary is, of course, the OED (Oxford English Dictionary), however I refuse to pay the exorbitant fee to join or the hundreds of dollars to purchase the multi-volume set. That would probably be your best bet to see if it's ever been used before.
Sufficient should suffice when an adjective is needed.
Well www.wiktionary.org does not recognize it, but, that is only one dictionary site, there are many out there, and I am sure it is listed in one of them, but I am not in the hunting mood right now. Lol Got to get busy packing and finding out how much a storage thing is going to set me back. Then I will get that taken care of then hunt, like for eggs, lol, just kidding.
I would think it's a word. I use it in everyday life. If it's not then shame on Webster's Dictionary. I like the sound of it. It's quite sufficive:)
Hi! I hope this helps; it's straight from Miriam Webster's. Main Entry: suf·fuse Pronunciation: www.m-w.com/mwref">sə-ˈfyüz Function: www.m-w.com/mwref">transitive verb Inflected Form(s): suf·fused; suf·fus·ing Etymology: Latin www.m-w.com/mwref">suffusus, past participle of www.m-w.com/mwref">suffundere, literally, to pour beneath, from www.m-w.com/mwref">sub- + www.m-w.com/mwref">fundere to pour Date: 1590
www.m-w.com/mwref">synonyms see infuse
— suf·fu·sion -ˈfyü-zhən noun
— suf·fu·sive -ˈfyü-siv, -ziv adjective