Shazam/Prime

Shazam is one of the most classic and rarest powerhouses in the game. In addition to his long stretch of health, Shazam packs a powerful punch, and can easily decimate entire teams. He also used to have the highest amount of health for the longest time, before being surpassed by Darkseid/Apokolips (1100, 1400) and Green Lantern/Red Lantern Hal Jordan (900, 1400) as of the 2.6 update, and with the 2.8 update,  Wonder Woman/Dawn of Justice (1100, 1400).

Strategy
He is most notorious for his passive, which allows him to use Bolt of Zeus and/or Roaring Strike for 12 seconds (up to 4 times) without using his power, (although his super move only does 20% of the normal damage), which can deal up to nearly 300,000 free damage if you use it right even prior to modifiers such as gear and teammates.

For 12 seconds after using his super, Shazam will retain two bars of power even after using a special, and he is not affected by most power drain effects from specials, ironically. It is possible to gain further power in this state (at a greatly reduced rate), possibly even using another super, but this has little point as his super only does 20% of the normal damage. All power will be removed after the buff wears off - including any power he gains during the passive.

His basic damage potential with his passive is often understated, in a small part because of the inaccuracy of the description - it actually increases his basic damage by 400% (i.e. his basic attacks will deal 5 times as much damage as normal barring other effects). While this stacks additively with other boosts and diminishes comparatively when stacking basic damage gear, this can still more than double his basic damage at near max gear scores, allowing his heavy combos to have a damage output rivaling his special 2.

Additionally, since his special 2 becomes unblockable if used right after his heavy combo, it could be used to great effect during his passive.

Shazam used to have the highest health in the game, until Doomsday/Containment surpassed him with 1500 effective health (600 base). He was then the character with the highest maximum health in the game in a single bar (since healing Containment Doomsday scales with his base maximum health, 600), until he was surpassed by Scorpion/Mortal Kombat X. He was still the character with the highest base health (as MKX Scorpion's health is tied to his passive and requires promotions) until surpassed by Red Lantern Hal Jordan. However, since Red Lantern Hal's passive causes him to take percentage max health damage to use specials or supers and he cannot be healed, it can be argued Shazam was not truly surpassed until the release of Darkseid/Apokolips (1400). For a very long time, he also has the highest total base stats, until surpassed by Batman/Arkham Knight and The Flash/Metahuman.

His popularity gradually declined as more and more new and powerful characters are released with less avoidable damage. The changes to blue lantern ring also affected him, as it could now only heal himself rather than the whole team by spamming Roaring Strike.

Offense
Getting to three bars is often a pain, as his light basic combos are rather awkward, and while his heavy combo is fast and easier to use, it also only deals 2 hits so he gains power much slower. Killing Joke Joker, Batgirl/Prime and Ra's Al Ghul's Scimitar can help with this issue. As for power generation gear, The Ibistick gives the greatest power generation of any gear (recently surpassed by League of Assassins Adept Knives), as well as giving him a large damage boost to both specials. If you don't have it (or if you want to stack more power generation) try Raven or Shazam's own specific gear, the former offers crit on s2 while the latter has stun on s2, both of which can be useful (the latter also has Area Effect on s1, although that is not quite as useful).

As his super allows him to do his s2 4 times in a row, Superman, Cyborg or Martian Manhunter's specific gear (increased max health and heal on s2) is very useful, allowing you to almost completely recover health with one super.

Defence
In order to counter Shazam, power drain is recommended to handle him, draining him before he can reach 3 bars. However, when you are on offense, it is very unlikely for Shazam to build up to three bars of power (watch out for Killing Joke Joker however, who is a classic combination with Shazam), and dealing with him is usually fairly straightforward, with the only problem being his very high base health, so he would heal quite a lot repeatedly with heal on s1 gear.

If he does use his super move, block gear would be very useful in mitigating the incoming damage, as he has no trick to get around block, and block gear can reduce his special damage to just 10% of the normal value. Be very careful when dealing with him during his passive; his personal gear grants him stun chance on special 2, so it might leave you open to yet another special.

Shazam, along with Darkseid/Prime and Superman/Godfall, were often used together as an online defence team. While their passives are not very useful for online defence and they have almost no synergy with each other, their very high base stats will attract many attacking teams, as the matching system will try to match players against stronger defence teams, allowing you to gain more battle rating. This has since become mostly obsolete due to the 2.6 update that introduced 3 new characters whose base stats surpass even Shazam and 2 more that tie with him.

Interactions
Please note that battles are highly situational: this section only mentions cards that have mechanics that, for any reason, are particularly effective with/against, or particularly ineffective against Shazam. Having a card that "counters" Shazam does not mean it is always a good choice.

Good with

 * The Joker/The Killing Joke: His passive grants his teammates full power when he is knocked out.

Countered by

 * Power Drain characters like Nightwing, Lex Luthor, Martian Manhunter, Green Arrow. Note that during Shazam's passive, he is immune to most forms of power drain, but Ra's Al Ghul's Dagger, Sinestro/Antimatter and Black Adam/ Kahndaq will drain his power, causing him to fall below the otherwise unmovable two bars of power. However, be warned that trying to basic attack him during his passive will leave you wide open for his specials.
 * Aquaman/Regime: Upon using his Super Move, he drains the entire enemy team of all power. It is currently unknown whether this works during Shazam's passive.
 * Raven/Prime: Shazam entirely lacks a one-hit nuke required to deal with Raven's extraordinarily powerful health swap passive as his super only does 20% damage, and the rapid-fire indiscriminate damage of the subsequent Roaring Strikes is exactly what Raven preys upon.
 * Green Lantern/John Stewart: Similar to Raven, except less devastating but extends the effect to his whole team; the four-second invulnerability for each character stops Shazam dead in his tracks and wastes at least a third of his passive.
 * Hawkgirl/Regime: She disables specials upon tagging in, preventing Shazam from using his specials or super at all for 5 seconds.
 * Zod/Man of Steel : His passive allows him to take a fairly large amount of damage off of Shazam's special 2, so you have to use more time to knock him out, resulting in you having less time to use your special 2 on other opponents.
 * Batman/Dawn of Justice : his passive allows him to "dodge" Shazam's specical, thus wasting away his precious power.
 * Black Adam/Kahndaq : despite won't be powerdrained by his specials, since Black Adam can also power drain his opponents upong using his combo-ender, thus, it can limit Shazam's effectiveness.

Abilities
Here are Shazam's abilities.

Support Cards and Gear
Here are Shazam's support cards and gear.

Trivia

 * The animation of the last hit of Roaring Strike (a bolt of lightning from above) is very similar to Solomon Grundy/Regime and Solomon Grundy/Prime's passive revival animation.
 * After using his super, it is actually possible to use another super before his passive wears off. This has no practical uses however, as the bonuses do not stack, his super does only 20% damage and power generation is greatly reduced after using his super (and using 2 supers in rapid succession will stop it entirely).
 * There was previously a bug that causes the flowing lightning effect to spread from the lighting bolt on his chest to his entire model, and it was fixed by the 2.6 update; despite this, it may still occur if you're playing on older devices.