I have probably listened to Emotionless Passion (Kazuya's theme) more than any other track in gaming history at this point with all of the times I've played it on YouTube. It just suits every aspect of his character so perfectly, and the darkness temple stage certainly complements the grave, foreboding atmosphere that the music conjures up.
Be in the Mirror (Devil's theme) also deserves special mention due to its uniqueness among boss themes. The slow pace, sullen tone, and emotional, mood-driven feel distinguish it from the intense, frantic, and furious themes that generally characterize most finales in fighting games. It is a stirring and quite saddening expression of the tragedy that has befallen the Mishima family and will continue to plague them and those who associate with them for countless years.
Instrumentally, The Headshaker (Yoshimitsu's theme) is probably among the most impressive, with a very rich and aesthetically pleasing mixture of resounding voices, strings, winds, and a host of other sounds that are relaxing and have the effect of really drawing one into the vivid imagery of the wilderness of feudal Japan.
There are many others worth mentioning, including Here is the Point of No Return (Armor King), Ancient Temple (Kunimitsu), Eastern Dance (Baek), Miracle Big Crushing Fist (Paul), As Bald As (Heihachi), and The Place, 1997 (Lei). Those are all personal favorites of mine, but it's really hard to decide which one is best; Tekken 2 has the best soundtrack in the series all around, with songs that are both instrumentally polished and highly diverse. It's one of those games that cast aside the issue of quality almost completely and make the question of which tracks are the best purely a matter of musical preference.
Black Winter Night Sky (for Opening PlayStation Movie)
Are You Ready? (for Character Select)
Paul's Miracle Deathfist (for Paul Phoenix Stage)
Nobody Catch Me (for Michelle Chang Stage)
Morning Field (for Jun Kazama Stage)
Forest (for Jun Kazama Ending)
Hit Out (for Bruce Stage)
More Vigorously (For Alex & Roger Stage)
