This may sound kind of lame but for most of the big bad single pokemon bosses you just need to have a solid team, while of course keeping in mind that you're going to have to face things like pulses and dittoceus :x. For example my team for the fight was Meowstic (Dual Screens until I eventually got Reuniclus), Greninja, Tangrowth (Great physical tank for chomp, can set up leech seeds), Volcorona (You cannot plan around this one since it is luck based but quiver dance did well against Abra) Mamoswine, and finally Dragalge who can tank specially pretty well.