controversial (adj.)

• arguable
• argumentative
• belligerent
• combative
• confutable
• conjectural
• contentious
• contestable
• controvertible
• debatable
• deniable
• dialectic
• disputable
• disputatious
• doubtable
• doubtful
• dubious
• dubitable
• eristic
• factious
• iffy
• ill-humored
• litigious
• mistakable
• moot
• polemic
• polemical
• problematic
• provocative
• quarrelsome
• questionable
• refutable
• scrappy
• speculative
• suppositional
• suspect
• suspicious
• unsettled