use '?' for JOKER (blank)

From letters K, I, N, D, E, R, G, A, R, T, N, E, R  I made following words

13 letter words

kindergartner[19]

12 letter words

kindergarten[18]

10 letter words

intergrade[12], retreading[12], interregna[11]

9 letter words

darkening[15], endearing[11], engrained[11], grenadine[11], earringed[11], grenadier[11], rereading[11], rendering[11], derringer[11], denigrate[11], gratineed[11], integrand[11], tendering[11], regranted[11], retarding[11], deterring[11], reearning[10], entrained[10], argentine[10], tangerine[10], irredenta[10], retrained[10], retearing[10], rerenting[10], entrainer[9]

8 letter words

kneading[14], gennaker[13], darkener[13], tinkered[13], retaking[13], ankerite[12], tinkerer[12], regained[10], endanger[10], deranger[10], gardener[10], garnered[10], deringer[10], derating[10], gradient[10], redating[10], treading[10], trending[10], garreted[10], gartered[10], regrated[10], regainer[9], drearier[9], antigene[9], detainer[9], retained[9], gratinee[9], interage[9], indenter[9], intender[9], interned[9], entering[9], interred[9], trendier[9], retarder[9], retainer[8], inerrant[8]

7 letter words

dekeing[13], darking[13], keening[12], kneeing[12], kneader[12], nakeder[12], reinked[12], reeking[12], narking[12], ranking[12], kerning[12], knarred[12], drinker[12], tanking[12], traiked[12], karting[12], neatnik[11], retaken[11], keratin[11], kernite[11], retaker[11], deaning[9], engined[9], needing[9], angered[9], derange[9], enraged[9], grandee[9], grenade[9], deraign[9], gradine[9], grained[9], reading[9], dreeing[9], energid[9], reeding[9], reigned[9], darning[9], grinned[9], rending[9], regrade[9], gnarred[9], grander[9], grinder[9], regrind[9], agented[9], negated[9], denting[9], tending[9], triaged[9], dragnet[9], granted[9], darting[9], trading[9], adenine[8], reginae[8], nardine[8], aginner[8], earning[8], engrain[8], grannie[8], nearing[8], readier[8], drainer[8], randier[8], dernier[8], nerdier[8], angrier[8], earring[8], grainer[8], rangier[8], rearing[8], grinner[8], dentine[8], anteing[8], antigen[8], gentian[8], grantee[8], greaten[8], negater[8], reagent[8], antired[8], detrain[8], trained[8], granite[8], gratine[8], ingrate[8], tangier[8], tearing[8], integer[8], treeing[8], regnant[8], ranting[8], renting[8], ringent[8], retread[8], treader[8], greater[8], regrate[8], tardier[8], tarried[8], retired[8], retried[8], tireder[8], granter[8], regrant[8], tarring[8], arenite[7], retinae[7], trainee[7], entrain[7], interne[7], tearier[7], terrane[7], retrain[7], terrain[7], trainer[7], reinter[7], rentier[7], terrine[7], tarrier[7], retirer[7], terrier[7]

6 letter words

deking[12], kinged[12], gained[8], ending[8], ginned[8], aedine[7], ennead[7], indene[7], innage[7], engine[7]