Raditz can be resumed as a weak character with pretty good Blasts 2 (each one costing 3 Ki Bars).
His best shot is his Blast 2-1, Full Power Energy Blast Volley. Use and abuse it. His other Blast 2, High Power Rush, is a bit weaker. It has long reach, pummels the ennemy on the spot, then smash him into the ground. It can be useful if ennemy is above or under you, safe from Full Power Energy Blast Volley.
Max Power Mode isn't a big deal for Raditz. His Ultimate Blast, Full Power Energy Wave, is a simple energy beam, without anything particulary appealing. Two other options are possible : use Max Power Combo or Violent Rush + Hyper Smash + additionalHoming Dragon and Banishing Attack, then Full Power Energy Blast Volley.
Concerning Blasts 1, Raditz has Saiyan Soul and Full Power. Both cost 2 of 3 Blast Stocks. But since Raditz is better in Blasts 2 than in Max Power Mode or melee, it can be useless.
In melee, Raditz has nothing particular. He has only one counter-attack, Body Strike, used while rushing, Sonic Impact and Giant Throw. Standard attacks are weaker than average, except Simple Ki Blasts and Throw.
Thus, Raditz is definitively better at Blasts 2.
An alternative rely only on melee, using Saiyan Soul then Violent Rush and Hyper Smash, but it is not optimal since Raditz has below than average Attack. However, since Attack +19 is a good item for his Great Ape form, the Base form benefits as well from this item, making this combo a valuable, but not the best, strategy. All in all, you can also spam Full Power Energy Blast Volley until you reach full 3 Blast Gauges, then use Saiyan Soul then the combo, never using a Blast move again (except for the final blow). The Blast 2 spam is anyway safer and stronger option.
Like all giants, Great Ape Raditz is a slow powerhouse. His best advantages are obviously his giant form, preventing him to be hit by Rush Blast Moves, and his high Attack.
However, Great Ape Raditz has no counter-attacks, unlike other giants, making him far more vulnerable against ennemys with high stun ability than other giants.
His Blast Moves are Chou Makouhou (4 Ki Bars) and Giant Rock Throw (3 Ki Bars) ; only one-hit straight attacks. His ultimate is Chou Makousen, a sweeping beam. These moves are indeed powerful, especially if they are boosted by Blast 2 +19, which is great for Base form Raditz ; but they are also easily avoidable if ennemy stays at distance, or is good at dodging Blasts Moves.
Support moves are Howl (2 Blast Stocks) and Sleep (3 Blast Stocks). Sadly, Great Apes are just too big to hide in corner and use Sleep, and Blast Moves aren't Great Ape Raditz's best aspect.
Like almost all melee characters, best way to defeat the opponent is to get onto ennemy's back (either by using High Speed Movement or Rolling Hammer and spamming Heavy Finish, the "4xA version". Or to use Air Combos.